EU referendum: Barack Obama says 'world needs Britain's influence in Europe to continue' as UK visit starts

The US President is expected to make an intervention supporting a vote to remain in the EU

US President Barack Obama steps off Air Force One upon arrival at Stansted Airport on April 21, 2016 in London, England. (Getty Images)

Barack Obama has called on Britain to stay in the European Union as international allies “stick together” against the challenges of terrorism, conflict and migration.

“The European Union doesn’t moderate British influence – it magnifies it,” he wrote in the Daily Telegraph.

“A strong Europe is not a threat to Britain’s global leadership - it enhances Britain’s global leadership.

“The US and the world need your outsized influence to continue – including within Europe.”

Barack Obama with Angela Merkel, the German Chancellor (Getty)

The US President arrived for a three-day visit to the UK late on Thursday night and is scheduled to meet David Cameron, have lunch with the Queen and go to Kensington Palace for dinner with the Duke and Duchess of Cambridge.

The timing of his trip across the Atlantic sparked accusations that the Prime Minister had asked him to intervene in the EU referendum debate, or as Eurosceptic Iain Duncan Smith put it, “bully the British people into making a decision”.

Mr Obama acknowledged the controversy, wryly “confessing” that he wanted to wish the Queen a happy 90th birthday in person.

“Ultimately, the question of whether or not the UK remains a part of the EU is a matter for British voters to decide for yourselves,” he wrote.

Hailing the “special relationship” between the US and the UK, the President characterised Britain as his country’s strongest link with the EU and said co-operation would be “far more effective” without a Brexit.

But in a counter-attack in The Sun, Boris Johnson accused Mr Obama of “incoherent” hypocrisy.

“For the United States to tell us in the UK that we must surrender control of so much of our democracy – it is a breathtaking example of the principle of do-as-I-say-but-not-as-I-do,” said the Mayor of London, who is campaigning for Vote Leave.

He dismissed arguments that Britain’s membership of the EU made it a stronger ally for America, claiming the 28-nation bloc was “stifling democracy”.

Speaking ahead of the President’s visit, Mr Cameron said they would be working on urgent challenges including Isis and conflicts in Syria, Iraq and elsewhere.

Human smuggling, Libya, Afghanistan, Ukraine and sanctions against Russia are also among the topics on the table.

But the pair are also expected to discuss the 23 June referendum ahead of a highly anticipated public intervention by the US leader.

A petition to prevent Mr Obama from giving a speech on the issue during his visit to Westminster had received almost 35,000 signatures by Friday morning.

Responding with a statement, a spokesperson for the Government said: “It is an established convention that members of either House can invite whoever they wish and in whatever capacity, to Parliament, to discuss and speak on a wide range of issues.”