John Prescott's alleged remark that President Bush was "crap" on peace in the Middle East has been dismissed by Tony Snow, a White House spokesman.
Mr Snow conceded the president may be called "piquant names"
"The president has been called a lot worse and I suspect will be," he said.
The deputy prime minister insists the reports of his comments in a private meeting with MPs are inaccurate.
But prominent Labour figures such as Ken Livingstone and Glenda Jackson have backed him regardless, with both saying American policies are a "disaster".
Mr Snow gave a pointed response to reporters when questioned on the matter, saying: "The president talks regularly with Prime Minister Blair, who is the prime minister.
"Prime Minister Blair has made it clear: he is going to remain a firm ally to the United States in the war on terror."
He said both men "have taken some hits" in the polls but saw their primary obligation as protecting national security.
Mr Prescott's biographer, Colin Brown, conceded the alleged remarks were "not diplomatic", but many people were "cheering him on" as a result.
This appeared to be borne out by quotes in the Independent newspaper from several Labour MPs.
Among them was Mr Livingstone, London's mayor, who said the current US administration had been "a disaster for the American people and has done untold damage, not only to international relations but to the environment".
Mr Prescott alleged views were "entirely endorsed" by Ms Jackson, who represents Hampstead and Highgate in north London.
"This government is failing miserably as far as our approach towards the Middle East is concerned," she said.
"We are simply... bag-carriers for Bush and all his policies have been a disaster."
And Ian Davidson, MP for Glasgow South West, told the newspaper that the deputy prime minister should be "commended for the quality of his political analysis."
He went on: "Britain has got to ensure that it is no longer seen as simply being the glove puppet of the United States."
Labour MP Harry Cohen said Mr Prescott's remark came during a private, "robust" meeting on Tuesday during talks with Muslim MPs and other Labour parliamentarians who represented large Muslim communities.
Mr Prescott said reports about his remarks were "inaccurate"
He said he believed Mr Prescott's comment had been "an honest and good point, well made", and was specific to the US efforts on the so-called "road map" for peace in the Middle East.
It was not a view of President Bush generally, the Bush administration as a whole, or the Bush administration's general Middle East policy, he added.
Mr Prescott has been Tony Blair's deputy since he came to power in 1997. Mr Blair is on holiday at the moment, leaving Mr Prescott in charge of the government.