US president Barack Obama has hit back after Boris Johnson's comments about his "part-Kenyan" ancestry.
Mr Johnson said the removal of a bust of Churchill from Obama's office was seen by some as a sign of an "ancestral dislike of the British Empire".
The comments in an article for The Sun were branded "idiotic" and "deeply offensive" by Churchill's grandson.
Mr Obama made clear his admiration for Britain's wartime leader in pointed remarks at a press conference.
He did not mention Mr Johnson by name but said he had a bust of Churchill outside the Treaty Room - his private office on the second floor of his official residence.
"Right outside the door of the Treaty Room, so that I see it every day - including on weekends when I'm going into that office to watch a basketball game - the primary image I see is a bust of Winston Churchill," he said.
"It's there voluntarily because I can do anything on the second floor. I love the guy."
It had been in the Oval Office, he said, but: "There are only so many tables where you can put busts otherwise it starts to looks a little cluttered."
As the first African American president, he said, a bust of Martin Luther King would be "appropriate", to remind him "of all the hard work of a lot of people who somehow allow me to have the privilege of holding this office".
He added: "That's just on Winston Churchill. I think people should know that, know my thinking there."
Mr Johnson said he was "delighted" by Mr Obama's backing for Churchill, but did not respond to questions about whether he had been trying to suggest the US President had a grudge against Britain.
Speaking earlier on a visit to a fast food restaurant in his Uxbridge constituency, Mr Johnson said: "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 relation to Churchill's bust.
Churchill's grandson, Conservative MP Sir Nicholas Soames, who is campaigning for Britain to remain in the EU, called the article "deplorable" and "completely idiotic".
He told LBC Radio: "I like to think, possibly - I'm mad enough to think - that it was probably written by some little twerp who works for Boris. I can't believe that Boris would really have done something so stupid, but whatever it is it bears his name and it is deeply offensive."
Labour's shadow chancellor John McDonnell called for Mr Johnson to withdraw his comment, writing on Twitter: "Mask slips again. Boris part-Kenyan Obama comment is yet another example of dog whistle racism from senior Tories."
Former Liberal Democrat leader Lord Campbell of Pittenweem said Mr Johnson's comments constituted an "unacceptable smear".
But UKIP leader Nigel Farage defended the comments, saying: "I think Obama, because of his grandfather and Kenya and colonisation, I think Obama bears a bit of a grudge against this country."
Stories about the removal of the Churchill bust were described by the White House in 2012 as "100% false".
"The bust still in the White House. In the Residence. Outside the Treaty Room," a senior adviser said in a rebuttal.
A Churchill bust lent to President George Bush by Tony Blair was removed from the Oval Office along with other art lent to the Bush presidency after Mr Obama's 2009 inauguration "as is common practice at the end of every presidency", the White House said at the time.
A separate bust of Britain's wartime leader, that has been in the White House since the early 1960s, remains on display.
Mr Johnson said in his article: "No-one was sure whether the president had himself been involved in the decision", 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."
The London mayor, who penned a best-selling biography of Churchill, was born in New York but recently said he intends to renounce his American citizenship to prove his "commitment to Britain".