A television ad in which the speaker of the House, Nancy Pelosi, and a former speaker, Newt Gingrich, warn about the dangers of climate change may violate federal election law, according to two campaign finance lawyers.

The spot, which shows Ms. Pelosi and Mr. Gingrich seated on a couch in front of the Capitol, is being questioned because the California Democrat faces a primary election June 3 in her San Francisco district.

“It’s prohibited,” a Republican campaign finance lawyer, Jan Baran, said. He said the ad constitutes a “coordinated” expenditure on behalf of Ms. Pelosi’s campaign by the group sponsoring the ad, the Alliance for Climate Protection. Any ad of that sort distributed in a candidate’s district within 90 days of a congressional primary or general election is deemed a campaign donation, Mr. Baran said.

“She’s in the ad. That means it’s coordinated,” a Republican attorney who battles to overturn campaign finance laws, James Bopp Jr., said. “I’m a guy that specializes in loopholes. I don’t know of any loopholes.”

The ad has run about 300 times on national cable networks such as Fox News and CNN since its debut last month, according to Evan Tracey of TNS Media Intelligence, an ad monitoring firm.

“It even had network airings,” he said.

The Alliance, which was founded by Vice President Gore and is funded in part by his Nobel Peace Prize award, is a nonprofit corporation organized in the District of Columbia and headquartered in Menlo Park, Calif. Most corporations are barred from making donations to federal campaigns. According to Mr. Bopp, even an unincorporated group would be limited to a single $2,300 gift for the primary. “This is no doubt way over $2,300,” he said. The ad could also trigger a requirement for Mr. Gore’s group to report publicly on its donors, campaign finance lawyers said.

In response to questions about the legality of the ad, a spokesman for Ms. Pelosi put some distance between the speaker and the ad’s sponsors. “We were pleased to participate in the Alliance’s nonpartisan effort on climate protection,” the aide, Drew Hammill, said in an e-mail statement. “We didn’t coordinate with the Alliance and trusted they would run the ad only where it was proper and legal.”

A spokesman for the Alliance, Brian Hardwick, defended the legality of the ad. “This is clearly a nonpartisan issue ad that has a call to action to the public on climate change,” he said. “We are confident that this ad is in compliance with all rules.” The two speakers’ ad ran a few times this week but is currently not scheduled to run again, according to the Alliance.

Lawyers said the rules apply, regardless of whether the ads are intended to aid the campaign. “The reformers including Speaker Pelosi insisted on this blanket prohibition,” Mr. Baran said. “Well-meaning ads still violate the statute.”

“Pelosi has been a big cheerleader of all of this,” Mr. Bopp added. “I’ve been arguing that these rules were going to entangle a member of Congress when they’re simply doing their job working with a nonprofit group. Well, here it is.”

Mr. Gore’s group and Ms. Pelosi may soon find themselves adopting arguments conservatives have long made against the federal rules. “The only defense has got to be that it’s unconstitutional,” Mr. Baran said.

A San Francisco real estate agent who favors the impeachment of President Bush and Vice President Cheney, Shirley Golub, is challenging Ms. Pelosi in the primary.