We were almost finished editing Citizen Black, our documentary on the press baron and former Telegraph owner, Conrad Black, when my husband and directing partner, Rick Caine, turned to me and said, “What should we do next?”

Having just made the film about a committed Conservative, we wanted to rinse our palate and take a look at someone who shared our leftist ideals. Then it hit us: what about Michael Moore? We like his films, we like what he stands for, and we loved his Oscar speech. He has long had a soft spot for us Canadians; as fellow lefties, we were almost certain he’d participate in this film.

For better or worse, Mr. Moore has become the unofficial spokesperson of the left. Raised in the suburb of Flint, Mich., the son of car industry workers, he has crafted a remarkable career by challenging and exposing the ugly side, the hypocrisies of American society and political life, through a series of satirical documentaries.

He started with “Roger & Me” in 1989, which examined the massive layoffs in, and destruction of, his hometown by what was then the world’s largest corporation, and followed it with a scathing indictment of America’s gun-crazy culture in the Oscar-winning “Bowling for Columbine,” and in 2004 he attacked the Bush administration’s war on terror in “Fahrenheit 9/11.”

In the beginning, we thought we’d make a straightforward biography looking at Mr. Moore’s life. But somewhere along the way things changed. Our film gradually became an examination of his film-making methods, and the serious political debates they provoked. As firm believers in Mr. Moore’s political agenda, our decision to re-focus the film wasn’t an easy one. But as we kept having to remind ourselves, you can still be an old leftie without swallowing everything Michael Moore says wholesale.

May 2004: Mr. Moore’s film “Fahrenheit 9/11” was about to premiere in Cannes. It would be the perfect time to start talking to him. We told an editor who was working on the Conrad Black film that we’d be back in four days. We weren’t. The film ended up taking two-and-a-half years to finish.

We couldn’t get an interview in Cannes. Mr. Moore’s publicist said he was doing “limited” press. But we did make the press conference. Most of the talk surrounded Disney’s refusal to distribute “Fahrenheit 9/11” in America even though they’d given him $6 million in financing through Miramax. “Every person in the world, with the exception of Taiwan and Hong Kong — those are the only two places we don’t have a distributor — everybody else in the world can see this movie but America,” Mr. Moore said.

Meanwhile, he couldn’t buy the press he was getting at Cannes. Mr. Moore won the Palme d’Or and “Fahrenheit 9/11” went on to gross more than $220 million worldwide. It was a non-fiction juggernaut.

Back home, this was proving to be our most difficult film. Practically everyone we spoke to was nervous. All too frequently we tried to interview people — friends, colleagues, former and current employees — who refused to talk on camera but had plenty to say on the phone. A former producer explained: “There’s a great story about how he is impossible to work for and he’s an impossible person. That’s the story most of us would like to do. I just don’t want to do it.”

One woman who had worked with him positively hissed at me: “You’re not going to make me say anything bad about him. Why are you doing this film?” Then she slammed down the phone. I’ll say this again: we had no preconceived notions about what Mr. Moore’s colleagues and friends would say.

I honestly wanted to hear good things about Mr. Moore. I wasn’t out to do a hatchet job, using only right-wing pundits and detractors. But others did have preconceived notions about what our film was about, and surmised, incorrectly, that we had an agenda. We lost count of the number of times we had to say, “We’re not Republicans.”

Soon enough we realized we were taking on a taboo subject, a sacred cow, especially in the documentary world. You’re not supposed to take on “one of our own,” we were told. It’s because of Mr. Moore that documentaries are so popular today, went the common refrain. It was starting to feel a little lonely out there.

Once “Fahrenheit 9/11” was released, Mr. Moore arrived in Toronto to promote the film. I asked him in person for an interview, explaining that we were doing a documentary on him. He seemed flattered, but then spoke the words that are the kiss of death for journalists: “These guys [his publicists] know how to reach me.” With that, he disappeared.

Next stop: Flint, Mich., the town Mr. Moore made famous in “Roger & Me.” This entertaining film shows his repeated attempts to interview General Motors’ then chairman, Roger Smith, to get him to acknowledge the damage GM was causing in Flint by laying off thousands of workers even as the company posted record profits. The closest Mr. Moore gets to challenging Mr. Smith on film is a fractious seconds-long exchange at a GM Christmas party.

We arrived at the Showcase multiplex theatre the day “Fahrenheit 9/11” opened. Everyone has an opinion about Mr. Moore. Some people know him and love him. Others hate him and “what he has done to Flint.” I was surprised at the rift. I thought he would be a hero in his home town, but instead, it is a microcosm of how America feels about him. He’s a polarizing force. Organizer of the Flint Film Festival, Greg Fiedler, told us: “We took a big hit for that movie, economically. A lot of companies that might have located here said ‘we’re not going there, they eat rabbit.'”

This is a reference to a scene in “Roger & Me” in which Mr. Moore visits an impoverished local woman, Rhonda Britton, whose roadside sign reads: “Rabbits for Sale, Pets or Meat.” She is seen skinning a rabbit to sell for food and the scene is meant to be emblematic of the economic problems that many Flint residents were facing. We began following Mr. Moore on his Slacker Uprising tour in the autumn, hoping to get an interview. This 30-day, 60-city tour through 20 swing states in advance of the American presidential election of November 2004 was Mr. Moore’s attempt to remove President Bush from power.

Our first stop was Syracuse, N.Y., outside the arena where Mr. Moore was speaking were groups of protesters. One side was anti-Moore, with “Moore Lies” and “Moore Emboldens our Enemy” signs. The other side was carrying placards reading “Troops out of Iraq” and “Bring the Troops Home Alive.” Inside the arena, Michael wound his way to the stage. He was surrounded by men he jokingly referred to as his “fitness instructors.” The sell-out crowd of 10,000 hung on his every word.

Mr. Moore’s ramped-up speaking style reminded me of an old-time preacher’s: the crowd was practically yelling “Amen” after every point he drove home. He’s a natural comic, honing his delivery with each new university he visits. He ranted to the students about Mr. Bush. “Shouldn’t we be able to believe the President of the United States? Is that too much to ask for that what comes out of his mouth is the truth? Of course some people would say Clinton lied, right? Exactly … about a blow job.” By the end of the night, he was urging every student to vote and dethrone Mr. Bush in the 2004 election.

During the tour I wrote to Mr. Moore’s lawyer, Andrew Hurwitz, asking for an interview. Nothing. At some point during our filming of Mr. Moore’s appearances, things became more difficult. In Detroit, a security team unplugged our sound equipment to keep us from recording his speech.

Mr. Moore has repeatedly encouraged people to “tape anything you’d like,” saying “I don’t agree with the copyright law.”

With this in mind, my producing partner, Rick, approached the guards for an explanation of why we were unplugged while other camera crews were not. Initially the bodyguard spoke into the microphone in his sleeve, attempting to get a serious answer, but inevitably dismissed us with a non-explanation: “I don’t know the answer to that. The only thing I have the answer to is me saying no. I’m also being told if you continue to bother and harass us about it you’re gonna be asked to leave.” Fortunately the guard didn’t see the other, smaller camera I used to tape this exchange.

We jumped in our car and drove from Toronto to Kent, Ohio, the site of one of the most notorious crackdowns on dissent in American history. In 1970, Kent State University students were protesting against the American invasion of Cambodia and four students were killed while nine others were wounded by the National Guard.

Mr. Moore’s publicist for the tour, Terri Hardesty, handed out copies of his books and DVD, then announced that Mr. Moore had a “very special guest tonight.” It was Roseanne Barr. The pair sat at a table at the front of the small room backstage in the university’s packed auditorium. Mr. Moore began taking questions.

At one point I told him what had been happening to us while following him on the tour. He appeared genuinely surprised. I asked again for a sit-down interview. He said that it wouldn’t happen now because he had only one mission between then and election day, November 2: to get Mr. Bush out of office. Perhaps after the election he would do something with us.

The press conference ended and we went into the main hall to tape his speech. A couple of minutes later, Mr. Moore’s sister Anne, Terri Hardesty, and some security guards showed up. From behind, Anne reached for Rick’s camera and shoved it. Another guard took our second camera off the tripod and shut it off — or so she thought. The camera actually carried on working, so in our film you get to see what happened next.

Anne said to the guards, “Escort them out of here.” The guards escorted us from the building, where we were consoled by supporters of the independent presidential candidate, Ralph Nader — they had left the speech earlier.

Being kicked out of the arena was surprising. I thought that after I had talked with Mr. Moore during the press conference and let him know the problems we were having, he’d tell his people to back off. I never expected to get thrown out of Kent State.

Then, slowly, we started to discover things about his films that we never knew, the most startling being that Mr. Moore had got rather more access to Roger Smith than he let on in “Roger & Me.”

We spoke to a man called Jim Musselman, a former activist for Mr. Nader, who was organizing the community of Flint to fight back against General Motors, and claims that Mr. Moore did question Mr. Smith for 15 minutes during a General Motors expo at the Waldorf Astoria in New York. “He sat there and answered questions for about 10 or 15 minutes,” said Mr. Musselman, who told us that he had watched the footage himself, in the “Roger & Me” edit suite. “It was great footage because it was Smith answering questions one-on-one from Michael.”

Then I found an article from a 1990 issue of Premiere magazine in which several people, including Mr. Nader, assert that Mr. Moore had also filmed an exchange with Mr. Smith at a 1987 General Motors shareholders’ meeting; that was reportedly left out of the film, too.

The magazine published a transcript of the exchange, which was mostly about taxes. Indeed, Mr. Moore told Premiere that he was at the meeting representing a tax-abatement group, not as a film-maker. “Nowhere in the transcript does it say anything about me asking him to come to Flint,” he said. “That’s the narrative thread of the movie.” This last point is open to debate: one original poster for “Roger & Me” depicts Mr. Moore pointing a microphone at an empty chair.

Though we didn’t want our documentary to concentrate solely on debunking Mr. Moore’s work, we did find other incidents that deserved a second look. In “Bowling for Columbine,” for example, Mr. Moore comes out of a bank carrying a gun he had got after opening a bank account. The viewer was given the impression that you could open an account and the bank would give you one of the guns it had in its vault. Just like that.

But in our film, Jan Jacobson, the bank employee who had helped him to open the account, maintains that she told Mr. Moore’s crew that the bank would have to do a background check and he’d have to pick up the gun from a licensed firearms dealer another day. Ms. Jacobson told us that Mr. Moore’s crew insisted the gun be in the bank for him to take away the same day. Mr. Moore was told that the guns were in a vault 300 miles away, but in the film he omits to mention this point. The result is a memorable scene which has Mr. Moore walking out of the bank holding up a gun after opening an account.

Or there’s “Fahrenheit 9/11,” in which Mr. Moore uses the following snippet from a speech to show Mr. Bush as the moneyed, arrogant man I’d assumed him to be: “This is an impressive crowd, the haves and the have mores. Some people call you the elite, I call you my base.”

I thought Mr. Moore had nailed Mr. Bush when I saw that. But Mr. Moore fails to mention that Mr. Bush is speaking at the Al Smith dinner, a Catholic fundraiser at which politicians are expected to make fun of themselves. The quote is taken out of context; at the same dinner, Al Gore jokes about having “invented the internet.” When seen in its original light, the president comes off as a guy who is capable of self-mockery: surely that’s surprising enough in itself.

As for the claim in “Bowling for Columbine” that people in Toronto leave their doors open at night … well, I don’t, and I don’t know anyone who does.

We first screened the documentary at the South By South West film festival in Austin, Texas. The crowd was full of the same kind of people who were probably cheering “Fahrenheit 9/11” a few years ago.

Having included some of the criticisms of Mr. Moore in our film, we weren’t sure what the response would be. It was provocative. On the one hand, we had Mr. Moore supporters telling us we shouldn’t be attacking a man who does so much good. On the other, we had leftist activists applauding us for questioning him.

Mr. Moore has been given every opportunity to respond to the questions raised by my film. Thus far he has refused to comment.

At a recent event in New York, Mr. Moore was asked about our film, which we’d decided to call “Manufacturing Dissent.” “The Noam Chomsky film?” he replied, coyly referring to the Chomsky documentary “Manufacturing Consent.” The journalist who had asked the question persisted: “No. ‘Manufacturing Dissent,’ the film about you and your filmmaking methods.” But Mr. Moore claimed he knew nothing about it.

© Debbie Melnyk / The Sunday Telegraph