Mitt Romney on Wednesday disavowed comments by an unnamed aide that President Barack Obama doesn't understand the "Anglo-Saxon heritage" shared by the US and Britain, as the White House said Romney was "fumbling" foreign policy.
The Republican White House hopeful's campaign scrambled to deny that one of its operatives had told a British newspaper that Romney, unlike Obama, understands America's "special relationship" with Britain.
In the context of previous jibes that the Democratic incumbent, the first black leader of the United States, does not understand American values and business practices, the latest alleged comments were seen as racially charged, and Obama's re-election campaign decried them as "stunningly offensive".
But Romney spokesperson Amanda Henneberg said the British report was mistaken.
"It's not true," she said in a statement. "If anyone said that, they weren't reflecting the views of governor Romney or anyone inside the campaign."
The Daily Telegraph said it had interviewed two unnamed Romney advisers, one of whom said: "We are part of an Anglo-Saxon heritage, and he feels that the special relationship is special."
"The White House didn't fully appreciate the shared history we have," the source added.
Romney, interviewed later on NBC News, said he was "not sure" who the adviser was and disavowed his comments.
"I also believe the president understands" the special US-British relationship, Romney said.
"So I don't agree with whoever that advisor might be, but do agree that we have a very common bond between ourselves and Great Britain."
The British paper also quoted an adviser saying Obama is a "left-winger" who "doesn't value the Nato alliance as much. He's very comfortable with American decline and the traditional alliances don't mean as much to him."
The sources declined to be identified because they were told not to be openly critical of the president while Romney was abroad. Telegraph reporter Jon Swaine clarified later on Twitter that the Romney advisers were "members of his foreign policy advisory team."
The comments caused scandal just as Romney arrived in London to kick off a tour of Britain, Israel and Poland aimed at boosting his foreign policy credentials.
His campaign has said he won't attack Obama's record during the trip, deferring to a standing tradition for candidates not to criticise the US president while overseas.
But despite a weekend truce to honour victims of a shooting massacre in Colorado that left 12 people dead and dozens wounded, Romney's trip comes at a caustic point in the campaign more than three months out from the election.
The White House seized on the remarks as undignified and disturbing.
"Despite his promises that politics stops at the water's edge, governor Romney's wheels hadn't even touched down in London before his advisers were reportedly playing politics with international diplomacy, attempting to create daylight between the United States and the United Kingdom where none exists," Vice President Joe Biden said in a statement.
Senior Obama re-election strategist David Axelrod called the remarks "stunningly offensive," while the campaign sought to make a mockery of Romney's bid for foreign policy credibility.
"This is a case where there's a continuous fumbling of the foreign policy football here," Obama campaign spokesperson Jen Psaki told reporters.
"And it does raise the question as to whether Mitt Romney and his team are ready to have a serious conversation about foreign policy."
The Romney campaign hit back, saying Obama's campaign was using the dustup as a distraction ahead of the November election.
Biden invoked "an anonymous and false quote from a foreign newspaper to prop up their flailing campaign," Romney spokesperson Ryan Williams said.
"We have very serious problems confronting our nation and American families are hurting, yet the Obama campaign continues to try to divert voters' attention with specious shiny objects."
Romney meets Thursday with several top British officials, including Prime Minister David Cameron, and attends the opening ceremony of the Olympic Games on Friday. He then travels to Israel and on to Poland.