Fury from Vote Leave after Obama's intervention

He maintained he had not come to ‘fix any votes’ but as Britain’s ally, it was his duty to give his opinion and ensure that Britain magnified its place in the world.

He said the outcome of the June 23 in-out referendum was in the United States’ interest due to the country’s shared prosperity with Britain.

He said: “This is a decision for the people of the United Kingdom to make. I’m not coming here to fix any votes. I’m not casting a vote myself. I am offering my opinion, and in democracies, everybody should want more information, not less, and you shouldn’t be afraid to hear an argument being made.”

He said Britain should not leave itself in the position where it has to work out piecemeal trade deals with the US as they would always favour the Transatlantic Trade and Investment Partnership they are currently trying to broker with the EU.

In effect, without the wider market place the EU brings, Britain would be “sent to the back of the queue” on securing stand alone trade relations, he said.

Putting himself in the shoes of a British voter, he said he would be wary of cutting himself off from the market that takes 44 per cent of British exports.

In an hour long press conference held at the Foreign Office, President Obama gave a major boost to Mr Cameron’s campaign and earlier yesterday bookmakers Ladbrokes reported that 90 per cent of all bets placed in the last 48 were for Britain to vote to remain in the EU.

Paddy Power also cut its odds on Britain to remain in the EU from 4/9 into 4/11 - 73.33 per cent chance - after the President arrived in the UK in a bid to convince the British public to vote to stay.

However those fighting to leave the EU were unimpressed with the President’s intervention and attempted to knock down his arguments over the ease of trade and highlight his comments on the migrant crisis.

Co-founder of Vote Leave, the officially designated campaign group leading the out campaign, Richard Tice, said: “We don’t have a trade deal with the United States now because we’re members of the European Union.

“The proposed EU-US trade deal, TTIP, would be disastrous for British workers.

“Obama doesn’t have the authority to deny us a deal, as he will be long gone before any such proposals are on the table.”

Justice Minister Dominic Raab, another Brexit campaigner, responded to the President’s comment that uncontrolled migration in Europe was an issue of security for the US.

He said: ‘The President made clear that uncontrolled immigration into the EU is a threat to national security. I agree - that is why it is safer to take back control so that we can stop terror suspects from Europe coming into the UK.

“He argued that he thinks it is in America’s interests for the UK to stay in the EU but what is good for US politicians is not necessarily good for the British people.”

Mr Raab also highlighted a stream of criticism hurled at Mr Obama throughout Friday on the fact America would not entertain an agreement to give up sovereignty of the scale expected by the EU.

He said: “The US would not dream of opening its border with Mexico, so it is hypocritical for President Obama to insist that we do the same with Europe.”

London Mayor Boris Johnson said: “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.”

David Cameron used his address to paint a picture of close US and UK relations, which are enhanced by EU membership. He said the TTIP deal would add billions to both economies, and that the EU and US economic muscle had been flexed most effectively when administering sanctions on Iran to prevent it developing a nuclear weapon.

Mr Cameron said Britain has “never felt constrained” in strengthening its relationship with the US while being a member of the European Union.