Brexit campaign left reeling by Barack Obama

Campaigners for Britain to leave the European Union were struggling to regain the initiative on Sunday after US president Barack Obama doubled down on his warning about the economic consequences of a Brexit.

Speaking to the BBC before he left for Germany, Mr Obama said Britain could have to wait for up to a decade after leaving the EU for a new trade deal with the United States.

“It could be five years from now, 10 years from now before we’re actually able to get something done,” he said.

Mr Obama angered Leave campaigners on Friday when he said a post-Brexit Britain would be at “the back of the queue” in negotiating a trade deal with the US. He said on Sunday that Britain could not expect to receive better treatment than the EU in trade talks.

“The UK would not be able to negotiate something with the United States faster than the EU,” the president said. “We wouldn’t abandon our efforts to negotiate a trade deal with our largest trading partner, the European market.”

Leave campaigners sought to dismiss Mr Obama’s intervention as meaningless because he will be out of office in January and any post-Brexit trade deal would be negotiated by his successor.

On Sunday, Democratic presidential candidate Hillary Clinton, who is the favourite to win the election in November, also called for Britain to remain in the EU.

“Hillary Clinton believes that transatlantic co-operation is essential, and that co-operation is strongest when Europe is united. She values a strong British voice in the EU,” Mrs Clinton’s foreign policy adviser, Jake Sullivan, told the Observer.

Weird intervention

London mayor

Boris Johnson

, accused of racism when he suggested Mr Obama was anti-British because of his Kenyan ancestry, returned to the attack on Sunday.

Writing in the Mail on Sunday, Mr Johnson described the president's intervention in the referendum campaign as "weird".

“Barack Obama is entitled to his view and he is an honoured guest, but it is ridiculous to warn that the UK will be at the back of the queue for a free trade deal,” he wrote. “The UK has never been able to do a free trade deal with the US in the last 43 years – because we are in the EU.

“Negotiations are held up by absurd problems like the French restrictions on Hollywood movies or Greek hostility to American feta cheese. No one in the last 48 hours has come close to answering my point – it is very weird that the US should be telling the UK to do something they would not dream of doing themselves in a million years.”

Still smarting from Mr Obama’s intervention, Leave campaigners on Sunday sought to prevent another foreign political figure from joining the debate – on their own side.

French far-right leader Marine Le Pen has said she wants to come to Britain to campaign for a Leave vote. But Leave campaigners on Sunday called on the Home Secretary, Theresa May, to ban her from entering the country.

Vote Leave co-chairman Gisela Stuart said Ms Le Pen held “divisive and inflammatory” views and her visit would not be “conducive to the public good”.

Mr Obama’s final official visit to the UK as president included a town hall-style meeting with 500 young people in Westminster, during which he called on the two communities in Northern Ireland to embrace a common identity.

He told Cliona McCarney (21), from Belfast, that he was encouraged by the fact that more children from the two communities were being educated together.

Northern Ireland

“You know better than I do,” the president said, “but one of the things you see in Northern Ireland that’s most important is the very simple act of recognising the humanity of those on the other side of the argument. That has taken time, but you are now seeing that among young people who are interacting more.

“It requires forging a new identity that is about being from Northern Ireland as opposed to unionist or Sinn Féin, just deciding the country as a whole is more important than any particular faction or any particular flag.”