Republican presidential hopeful Rudy Giuliani has been criticised over a fundraising party at which participants are being urged to donate $9.11.
The International Association of Fire Fighters accuses him of exploiting the 11 September 2001 terrorist attacks.
Mr Giuliani rose to national prominence as New York's mayor on 9/11.
The Giuliani campaign says it did not plan the event, which is due to take place on Wednesday evening in California at the home of a supporter.
Nevertheless, the firefighters association said the stated theme of the fundraiser - "$9.11 for Rudy" was in poor taste.
"It is nothing short of disrespectful to the legacy of the thousands of civilians and 343 brave firefighters who died at Ground Zero," said Harold Schaitberger, IAFF president.
Democratic presidential candidate Chris Dodd described the fundraiser's theme as "unconscionable, shameless and sickening."
A Giuliani campaign spokesman said the idea was selected without the campaign's knowledge.
But the host of the party, Abraham Soefer, also said the theme was not his responsibility, and referred other questions to Mr Giuliani's campaign team, the Associated Press reports.
The event is one of several Giuliani house party fundraisers across the US on Wednesday.
Mr Giuliani is seen as one of the frontrunners in the race for the Republican nomination.
But the BBC's Justin Webb, in Washington, says that Mr Giuliani's appeal as the man who led New York through the terrorist attacks is occasionally over-emphasised in his campaign.
This fundraiser looks like a big blunder, our correspondent adds.