US president Barack Obama's blunt warning that Britain would be at "the back of the queue" for American trade deals if it quit the EU has provoked a backlash from the Brexit camp.
Leading Leave campaigners accused Mr Obama of spouting Britain-bashing rhetoric at Downing Street's bidding in order to scare voters into the Remain camp.
The attack came after Mr Obama set out in stark terms that Britain would not be able to strike a free trade deal with the US "any time soon" if it leaves the EU because Washington's focus would be on reaching agreement with Brussels.
The president was speaking after Downing Street talks with Prime Minister David Cameron during a two-day visit which he has used to speak out in favour of continued UK membership of the 28-nation bloc after the June 23 referendum.
Ukip leader Nigel Farage said Mr Obama did not know what he was talking about, and was being manipulated by Number 10.
"He said Britain would be at the back of the queue, no American would ever say 'back of the queue', Americans don't use the word 'queue', Americans use the word 'line'," Mr Farage told BBC Radio Four's Any Questions.
"Therefore, what Obama said when he said we would be at the back of the queue, he was doing the bidding of Cameron, and Number 10, and doing his best to talk down Britain, and I think that's shameful."
Tory former defence secretary Liam Fox insisted that Mr Obama's views would be irrelevant after the looming US presidential election.
"We have a referendum at the end of June, presidential elections are in November, so whoever it is that will be at the helm of the United States won't be Barack Obama. So, to an extent, whatever he says today is largely irrelevant," he said.
"It will be the next president, and the next congress, who will be in charge of any trade arrangements.
"Why do we get trade arrangements? We get them because it is to the mutual benefit of both parties, and we have a roughly balanced trade with the United States. It would seem bizarre if we weren't able to take advantage of a trade relationship.
"We heard 'you are our best friend, we have a special relationship, and you will get a punishment beating if you leave the EU'. This is very much the Downing St refrain," Dr Fox told BBC2's Newsnight.
London mayor and prominent Leave campaigner Boris Johnson described the American stance as "bizarre".
At a joint press conference with Mr Cameron, the president stressed that the referendum was a "decision for the people of the United Kingdom" and he was "not coming here to fix any votes".
But he defended his right to offer an opinion, saying: "In democracies everybody should want more information, not less, and you shouldn't be afraid to hear an argument being made - that's not a threat, that should enhance the debate.
"Particularly because my understanding is that some of the folks on the other side have been ascribing to the United States certain actions we will take if the UK does leave the EU - they say for example that 'we will just cut our own trade deals with the United States'.
"So they are voicing an opinion about what the United States is going to do, I figured you might want to hear from the president of the United States what I think the United States is going to do.
"And on that matter, for example, I think it's fair to say that maybe some point down the line there might be a UK-US trade agreement, but it's not going to happen any time soon because our focus is in negotiating with a big bloc, the European Union, to get a trade agreement done.
"The UK is going to be in the back of the queue."
Mr Obama said that while the vote was a matter for the British people, the US had a "deep interest" in the outcome.
"The United States wants a strong United Kingdom as a partner and the United Kingdom is at its best when it is helping to lead a strong Europe," he said.
"It leverages UK power to be part of the European Union. I don't believe the EU moderates British influence in the world, it magnifies it. I believe the UK strengthens both our collective security and prosperity through the EU."
Mr Cameron said the referendum was the "sovereign choice of the British people" but added: "As we make that choice, it surely makes sense to listen to what our friends think, to listen to their opinion, to listen to their views and that's what Barack has been talking about today."