WASHINGTON – An internal strategy dispute among backers of President Bush’s Social Security proposal became a public row yesterday when one group supporting private accounts accused another of “bigotry” against gays.

USA Next, an activist group backing the president’s proposal for private Social Security accounts, has launched a $10 million ad campaign to discredit one of the most powerful critics of the proposed private accounts, AARP, a seniors lobbying group. The ads accuse the AARP of “liberal bias” and of supporting “massive government, oppressive regulations, high taxes, and anti-family policies.”

A USA Next ad that recently appeared on the Internet suggested AARP supports gay marriage and opposes American troops.

The decision to link Social Security accounts to gay marriage was blasted yesterday by another staunch supporter of Mr. Bush’s plan, the free-market Cato Institute.

The ads are “bigoted” and will “backfire” among young people, who are more likely to support gay marriage, said the Cato Institute, a free market think tank that helped pioneer the idea of personal accounts.

The campaign is a “great strategic blunder and wrong in principle,” said the director of Cato’s Project on Social Security Choice, Michael Tanner, in a scathing statement.

He said the ad’s message could undermine an ongoing effort among the accounts’ supporters to appeal to young voters, gay people, women, and racial minorities, he said.

“Cato and other pro-reform groups believe that the Social Security debate represents a tremendous opportunity for political bridge-building and for gays and ethnic minorities to feel included in the national debate over retirement issues,” Mr. Tanner said.

The dispute was not limited to policy groups, however. Senator Corzine, a Democrat of New Jersey, yesterday called on President Bush to denounce USA Next’s tactics.

“The motive for USA Next’s irresponsible use of such hot-button issues is not difficult to decipher – if you can’t attack the message, attack the messenger – no matter how dishonest and off-base those attacks become,” Mr. Corzine wrote in a letter.

Unbowed by the criticism, USA Next’s chief executive yesterday vowed to continue to portray AARP as “the largest left-liberal organization on the planet.

“We’re going to pound them mercilessly on their stands on issues,” Charles Jarvis told The New York Sun in an interview.

Mr. Jarvis, who worked for President Reagan and the first President Bush, has said his goal is to permanently cripple AARP and draw away 1 million members by persuading them that the group does not reflect their views.

The gay marriage Web ad that was pulled after a few hours was a “test” to see whether liberal advocacy groups “would explode about an image or deal with the content of the debate,” he said.

Despite the outrage it generated, Mr. Jarvis said the group would not shy away from running additional ads linking AARP to gay marriage.

“We are going to make sure their members know their positions on everything, including their position on gay marriage in Ohio,” he said.

AARP’s Ohio chapter had opposed a constitutional amendment banning gay marriage in that state.

A spokeswoman for AARP, Nancy Thompson, said the group is “not reacting” to the attack ads.

AARP does not have a position on gay marriage, she said. AARP Ohio opposed that state’s gay marriage amendment because part of the proposal would have “truncated certain rights” of people living in the same household who were not married, and that would have included many seniors, she said in an interview.

USA Next is a project of the United Seniors Association, a group that is funded by 1.5 million members and businesses that support free-market policies.

The group hired several of the same consultants who worked for the group Swift Boat Veterans for Truth, which attacked Senator Kerry’s military record in the presidential campaign.

In another sign that the Social Security fight is turning more aggressive and personal, a liberal activist group began an ad campaign to discredit the chairman of the House Social Security subcommittee, Rep. James McCrery, a Louisiana Republican, for having ties to financial services firms that could benefit from the plan.

The group, Campaign for America’s Future, has bought newspaper ads in Mr. McCrery’s district, claiming that he has accepted hundreds of thousands of dollars in campaign cash “from the very interests who will benefit the most if the president’s plan to privatize Social Security is passed.”

Mr. McCrery called the ads “a pitiful attack campaign,” in a statement.

Meanwhile, in Washington, Treasury Secretary Snow acknowledged yesterday that the Bush administration still had not succeeded in selling its Social Security plan to Americans.

“We still have some work to do,” Mr. Snow said.