Mr Trump, in an interview with ITV, said: "I don’t want to say front or anything else – I would treat everybody fairly but it would not make any difference to me whether they were in the EU or not.

"You would certainly not be at the back of the queue, that I can tell you."

Mr Trump confirmed that he would back a Brexit if he had a vote in the referendum on June 23.

He said: "I have no preference I have big investments in Britain but I have no preference. I think if I were from Britain I would probably, I would not want it, I would want to go back to the different system."

President Obama provoked a furious backlash from the Leave camp last month when he warned a post-Brexit Britain would be at the "back of the queue" when it came to a new economic agreement with Washington.