Boris Johnson has defended his attack on the "part-Kenyan" President Barack Obama, saying he did not imply the US leader was anti-British.
The Brexit-backing London mayor has come under fire for what critics have called "dog whistle racism" over comments referring to the president's ancestry, made in a newspaper column.
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Mr Johnson said it was "incoherent", "inconsistent" and "downright hypocritical" for the US leader to intervene in the European Union referendum row.
In an article for The Sun, the mayor also referred to the removal of a bust of Winston Churchill from the Oval Office when Mr Obama became president.
He said "no-one was sure whether the president had himself been involved in the decision" to remove the bust, adding: "Some said it was a snub to Britain. Some said it was a symbol of the part-Kenyan president's ancestral dislike of the British empire - of which Churchill had been such a fervent defender."
But asked if he intended to imply Mr Obama was anti-British, Mr Johnson said: "Not at all, not at all."
Speaking outside a Subway restaurant in his Uxbridge constituency, he added: "Well I think obviously people will make of the article what they want.
"The crucial point is that I'm a big fan of Barack Obama - I was one of the first people to come out in favour of him ages ago.
"But I think there's a weird paradox when the President of the Unites States, a country that would never dream of sharing its sovereignty over anything, instructs or urges us politely to get more embedded in the EU, which is already making 60% of our laws.
"I think the issue really is about democracy - America guards its democracy very jealously and I think we should be entitled to do so as well."
Downing Street said Mr Johnson was recycling "false" claims in referring to the bust.
Shadow chancellor John McDonnell called for Mr Johnson to withdraw the comment.
He said on Twitter: "Mask slips again. Boris part-Kenyan Obama comment is yet another example of dog whistle racism from senior Tories.
"He should withdraw it."
And Labour frontbencher Diane Abbott claimed Mr Johnson's "offensive" comments echoed those of the "Tea Party" right-wing tendency in the US.
Shadow international development secretary Ms Abbott said: "Boris dismissing president Obama as 'half-Kenyan' reflects the worst Tea Party rhetoric."
Former Liberal Democrat leader Lord Campbell of Pittenweem said Mr Johnson's comments were "an unacceptable smear".
He said: "Many people will find Boris Johnson's loaded attack on president Obama's sincerity deeply offensive. If this is an illustration of the kind of diplomacy that we might expect from a Johnson leadership of the Tory Party then heaven help us.
"In truth this attack constitutes an unacceptable smear."
Asked how David Cameron viewed Mr Johnson's comments on the president's "half-Kenyan" heritage, the Prime Minister's official spokeswoman said: "It is important to engage with the facts.
"If you look at the issue the mayor of London was talking about, which related to the bust of Churchill in the Oval Office, they have been clear that this suggestion that he asked for it to be moved and that it is a failure of the president's appreciation of the special relationship is false.
"That decision had already been taken before President Obama took office, so let's focus on the facts."
Sir Stephen Wall, former British permanent representative to the European Union, said: "Boris Johnson's comment implying the President of the United States is driven by his ancestral dislike of the British Empire is demeaning to the debate.
"Using that type of language does not reflect Britain's standing in the world or the country we aspire to be.
"As our most important ally, President Obama has the right to offer his view and he has made it clear that being in Europe magnifies British influence and enhances Britain's global leadership."
And former UK ambassador to Washington Lord Kerr said: "The US has an interest in Britain, its closest ally, being stronger, safer and better off in the EU - not weaker, out on its own.
"To claim that the American president has no right to say what he believes, and speak up for US political, economic and business interests, is typical Boris bluff and bluster."
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