WASHINGTON – Under fire for permitting third-party groups to funnel multimillion-dollar contributions into federal elections, the Federal Election Commission yesterday created new rules to restrict their activities beginning next year.

The so-called 527 groups, which critics call “shadow parties,” will no longer be allowed to use unlimited donations to pay for voter-mobilization drives or political advertisements if they raise more than $1,000 by telling their donors the money will be used to elect or defeat a particular candidate.

Political action committees will also be required to pay for at least half the costs of federal election activities – such as voter drives, political ads, direct mail that mentions candidates, and overhead costs – with money raised in small one-time donations, known as hard money.

“It’s not tinkering. It’s a big deal. I hope people can graciously accept that we are doing what people have been clamoring for us to do,” said the vice chairwoman of the commission, Ellen Weintraub, a Democrat appointed by President Bush.

But critics immediately denounced the rules as insufficient and condemned the commissioners for rejecting, on a vote of 4-to-2, a more sweeping proposal that would have subjected many of the groups to the stricter regulations that apply to political action committees.

“The FEC had the opportunity to meaningfully address the illegal use of soft money by 527 groups in federal elections and it refused to do so today,” said the president of Democracy 21, Fred Wertheimer. He dismissed the new rules as “an effort to create the illusion that this rogue agency was doing its job.”

A campaign finance lobbyist for Public Citizen, Craig Holman, said the rule “won’t capture any organizations except the most careless.”

Commissioner Scott Thomas cast a protest vote against the rules he called “tinkering.” Groups can easily skirt the rules by simply not telling donors that the money is intended to elect or defeat a particular candidate, he said.

“We’re going to see of course all sorts of solicitations just modified slightly so they’ll be saying things like, ‘We want the money to help defeat Bush’s policies,’ or ‘We’ll use your money to prevent four more years of Bush’s policies,’ or ‘Your money will be used to tell the truth about Kerry’s Vietnam service,’ “he said.

Mr. Thomas, a Democrat appointed by President Reagan, called on Congress to craft a stronger rule.

Several times during the televised hearing, Ms. Weintraub lashed out against the sharp criticism that has been aimed at the commission, blaming critics of creating a “poisoned” atmosphere and spreading misinformation.

She said prominent advocates of campaign finance restrictions are denouncing the very kind changes they had until recently advocated, and suggested that any proposal from her and Mr. Smith “is going to be greeted with howls of protest just because it’s got our names on it.”

“It becomes a very vitriolic and personalized debate where people are basically engaging in name-calling, and I regret it very much,” Ms. Weintraub said. She complained of “misinformation” in the press, and pointed to an opinion editorial in the New York Times that called the commission “a snoozing watchdog” that has “done nothing” to rein in groups such as MoveOn.org that has run television ads attacking President Bush’s National Guard record.

“Well, we checked, and those ads are being run by MoveOn’s federal pac, paid for by 100% hard dollars. I don’t know what more we can do short of censoring them. Does the New York Times want us to start censoring ads? I find that hard to believe. But that’s the sort of allegations that get tossed around here. People are assuming that anytime someone runs an ad it’s a bad thing, probably paid for by soft money, and oh, it must be evil. In fact, many of these ads are being paid for by hard dollars,” she complained.

Mr. Smith, a Republican who was appointed by President Clinton and has criticized tightened campaign finance laws, said he had “tremendous philosophical objections to what I just voted for,” but said his job is to uphold the law.

The commissioners said they did not plan any further rulemakings with regard to 527 groups, but said they would revisit the issue if new problems emerged.

Commissioner Danny McDonald, a Democrat appointed by President Reagan, voted against the rules and said the commission should delay a decision until after the November elections and hold public hearings on the issue, rather than making rules while it is under attack. “We’ll be in a better position after the political season is over to see what actually has transpired,” he said.