EU agreement allows for the free flow of citizens across member nations' borders; U.S. does not allow Mexicans to come over without papers

London Mayor Boris Johnson accused him of making an 'incoherent' and 'inconsistent' argument because the U.S. would never give up

A US-UK trade agreement is not going to happen 'any time soon,' Obama warned today

President Barack Obama told Britain today that it would have to 'go to the back of the queue' if it leaves the European Union, then tries to negotiate its own trade deal with the United States.

A US-UK trade agreement is not going to happen 'any time soon,' Obama said during a joint news conference with British Prime Minister David Cameron.

‘Not because we don’t have a special relationship but because given the heavy lift on any trade agreement, us having access to a big market with a lot of countries rather than trying to do piecemeal trade agreements, which is hugely inefficient,' the U.S. leader said.

Obama faced a furious backlash overseas this morning over what has been called a 'downright hypocritical' push for Britain to stay in the European Union.

In a highly controversial intervention in the EU referendum campaign, Obama pleaded with British voters in a local newspaper and then the press conference not to cut ties with Brussels.

'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,' Obama said during a news conference at Britain's Foreign and Commonwealth Office.

In his op-ed Obama also invoked the spirit of the Second World War by claiming the sacrifice of GIs meant America has a stake in the EU debate and said the decision in June's referendum 'will echo in the prospects of today's generation of Americans as well'.

London Mayor Boris Johnson accused him of making an 'incoherent' and 'inconsistent' argument.

A furious Johnson said this morning: 'The Americans would never contemplate anything like the EU, for themselves or for their neighbors in their own hemisphere. Why should they think it right for us?'

President Barack Obama told Britain today that it would have to 'go to the back of the queue' if it leaves the European Union, then tries to negotiate its own trade deal with the United States

A US-UK trade agreement is not going to happen 'any time soon,' Obama said. ‘Not because we don’t have a special relationship but because given the heavy lift on any trade agreement, us having access to a big market with a lot of countries rather than trying to do piecemeal trade agreements, which is hugely inefficient,' Obama said

Obama's visit is a welcome one for British Prime Minister David Cameron, who is leading the 'In' campaign. They're seen here heading into a meeting before their news conference

In a highly controversial intervention in the EU referendum campaign, Obama pleaded with British voters today not to cut ties with Brussels - saying it 'magnified' the UK's influence in the world. He and Cameron are seen here today on the steps of Number 10 prior to their meeting

FIT FOR A QUEEN: Britain's Queen Elizabeth II and the Duke of Edinburgh stand with the President and First Lady of the United States Barack Obama and his wife Michelle in the Oak Room at Windsor Castle ahead of a private lunch celebrating the Queen's 90th birthday

Obama faced a furious backlash overseas this morning over his 'downright hypocritical' decision to urge Britain to stay in the European Union, put it didn't appear to put a damper on this lunch with the Queen

Obama told residents of the UK today he doesn't believe he's overstepping.

Ultimately 'this is a decision for the people of the United Kingdom to make,' he told them.

'I'm not coming here to fix any votes. I'm not casting a vote myself. I'm 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, 'That's not a threat, that should enhance the debate.'

The U.S. president said he feels its his prerogative to clarify the U.S. position rather than have it defined by British politicians.

'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,' he said.

'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.

He added, 'The UK is going to be in the back of the queue.'

Obama brought up WWII and the international institutions the US and UK designed together including the United Nations, the IMF, the World Bank, and NATO.

'All of those in some degree constrained our freedom to operate and occasionally we had to deal with some bureaucracy,' he said, 'it meant that on occasion we had to persuade other countries and we don’t get 100 percent of what we want in each case but we knew that by doing so, everybody was going to be better off.'

He again the UK involvement in the EU 'magnifies' the nation's power - 'it doesn’t diminish it' and argued that 'divisions in Europe' would weaken NATO.

'That’ll have an impact on our collective security,' he stated. 'I have a confidence in the UK, and I know that if we are not working effectively with Paris or Brussels then those attacks are going to migrate to the United States and to London, I want one of my strongest partners in that conversation.'

Hitting back at his critics, Obama said, 'All of us cherish our sovereignty - our country is pretty vocal about that - but the US also recognizes that we strengthen our security through our membership of Nato, we strengthen our prosperity through organisations like the G7 and the G20.'

'I believe the UK strengthens both our collective security and prosperity through the EU.'

The Obamas arrived by helicopter outside Windsor Castle, west of London, today. Obama meanwhile plunged himself into Britain's increasingly poisonous EU debate at the start of a visit, warning strongly against Brexit and pointing out that US soldiers had died for Europe

HAPPY BIRTHDAY: After meeting the Queen at Windsor Castle for lunch to celebrate Her Majesty's 90th birthday, Obama will travel to Whitehall for meetings with government ministers

Anger at Obama was not limited to Johnson. Senior Members of Parliament who vented their fury at British Prime Minister David Cameron and Defence Secretary Michael Fallon over a warning that there would be celebrations by Moscow and the Islamic State ‘in Raqqa’ if the UK votes Brexit.

UK Justice Minister Dominic Raab said Obama was guilty of 'double standards' because he would 'not dream of opening the US border and allowing free movement with Mexico and he would not dream of allowing the U.S. Constitution to be trumped by a Latin American court'.

And he mimicked the U.S. president, adding: 'Can Britain do better outside the EU? I would have to quote Mr. Obama in saying, “Yes we can”.'

BORIS JOHNSON BRANDED 'RACIST' AFTER HIS ATTACK ON 'PART-KENYAN' BARACK OBAMA The Mayor of London (pictured outside his north London home this morning) spoke out against the U.S. president this morning Boris Johnson was accused of 'dog whistle racism' and likened to right-wing 'Tea Party' politicians in the U.S. this morning after his attack on the 'part-Kenyan' Barack Obama. The Mayor of London spoke out against the U.S. president after he urged British voters to stay in the EU and mentioned Obama's African ancestry as he criticized the decision to remove a bust of Sir Winston Churchill from the Oval Office shortly after Obama entered the White House. Johnson - who is favorite to succeed David Cameron as prime minister - suggested Obama got rid of the statue as a 'snub' to Britain's wartime prime minister and a 'symbol of the part-Kenyan President's ancestral dislike of the British empire'. UK Shadow Chancellor John McDonnell demanded Johnson withdraw the controversial remarks. He wrote on Twitter: 'Mask slips again. Boris part-Kenyan Obama comment is yet another example of dog whistle racism from senior Tories. He should withdraw it.' Johnson's team has yet to respond to MailOnline's request for comment. Diane Abbott, Shadow International Development Secretary, described Johnson's remarks as 'offensive' and said they echoed those of the Tea Party's right-wing, anti-immigration tendency in the U.S. Former Lib Dem leader Lord Campbell said Johnson's comments were 'an unacceptable smear'. 'Many people will find Boris Johnson's loaded attack on President Obama's sincerity deeply offensive,' Lord Campbell said. 'If this is an illustration of the kind of diplomacy that we might expect from a Johnson leadership of the Tory Party then heaven help us.' Referring to the removal of Sir Winston's bust, Johnson wrote in The Sun today : 'No one was sure whether the President had himself been involved in the decision,' he said. 'Some said it was a snub to Britain. Some said it was a symbol of the part-Kenyan President's ancestral dislike of the British empire - of which Churchill had been such a fervent defender.' Responding to the controversial remarks, Abbott said: 'Boris dismissing president Obama as 'half-Kenyan' reflects the worst Tea Party rhetoric'. Obama shed light on the matter at today's news conference. The bust now sits outside his personal office in the residence area of White House. 'It’s there voluntarily, because I can do anything on the second floor,' Obama said. 'I love Winston Churchill. I love the guy.' George W. Bush kept it in the Oval Office, Obama explained, but here are only so many tables where you can put busts, otherwise it starts looking a little cluttered.' 'And I thought it was appropriate, and I suspect most people here in the United Kingdom might agree, that as the first African-American President, it might be appropriate to have a bust of Dr. Martin Luther King in my office to remind me of all the hard work of a lot of people who would somehow allow me to have the privilege of holding this office.' Advertisement

But Peter Westmacott, Britain's former ambassador to the United States, hit back at the charges of hypocrisy. 'No one is asking the UK to surrender anything it’s got,' he told the BBC.

'What the president is saying is not telling people how they should vote; he is saying we are in a very important place as a member of the EU and we should think very carefully on turning our back on that.'

The US government - and many US banks and companies - fear a Brexit would unleash market turmoil, diminish British clout, undermine London's status as a global financial capital, cripple the EU and undermine Western security.

The president's intervention in the so-called 'Brexit' debate has already sparked criticism from some who say he is meddling in Britain's business.

Number 10 and the White House have orchestrated a pro-EU blitz to coincide with the U.S president's visit.

Obama said a vote to cut ties with the Brussels-based EU would leave Britain less able to tackle terrorism, the migration crisis and economic difficulties.

And he said Britain and America's 'special relationship was forged as we spilled blood together on the battlefield'.

Obama's visit was a welcome one for Prime Minister David Cameron, who is leading the 'In' campaign.

After meeting the Queen at Windsor Castle for lunch to celebrate Her Majesty's 90th birthday, Obama met with Cameron, Foreign Secretary Philip Hammond, Chancellor George Osborne and Home Secretary Theresa May in Downing Street before holding the joint press conference with the Prime Minister in the Foreign and Commonwealth Office.

President Obama has also invited Cameron to a private dinner in London, Downing Street said, but did not disclose the location or other guests.

Setting out his strong opinion in favor of Britain staying in the EU, Obama wrote in the Daily Telegraph today: 'I will say, with the candour of a friend, that the outcome of your decision is a matter of deep interest to the United States.

'The tens of thousands of Americans who rest in Europe's cemeteries are a silent testament to just how intertwined our prosperity and security truly are. And the path you choose now will echo in the prospects of today's generation of Americans as well.'

President Obama said the U.S., the UK and the EU 'have turned centuries of war in Europe into decades of peace, and worked as one to make this world a safer, better place'.

'What a remarkable legacy that is,' he wrote. 'And what a remarkable legacy we will leave when, together, we meet the challenges of this young century as well.'

The president also made an emotional appeal for Britain to vote to remain a part of the EU, which he says is an institution created 'from the ashes of war'.

'Our special relationship was forged as we spilled blood together on the battlefield,' he said. He compared the EU to the United Nations, Nato and post-war agreements such as Bretton Woods and the Marshall Plan.

'From the ashes of war, those who came before us had the foresight to create the international institutions and initiatives to sustain a prosperous peace,' he said.

'Their efforts provided a foundation for democracy, open markets and the rule of law, while underwriting more than seven decades of relative peace and prosperity in Europe.' President Obama argued that Britain's membership of the EU 'magnifies' its influence abroad.

'The European Union doesn't moderate British influence – it magnifies it,' he added. 'A strong Europe is not a threat to Britain's global leadership; it enhances Britain's global leadership.'

But his comments were met with anger from Eurosceptics. Former Cabinet Minister Iain Duncan Smith led a chorus of protest at Britain being told to accept open borders when the U.S. does not do the same.

Citizens of Mexico, part of the North American Free Trade Agreement with the U.S. and Canada, have no automatic right to enter America, in contrast to the 500 million EU nationals free to come to Britain.

Duncan Smith said: 'What I do find strange is that he is asking the British people to accept a situation he would not recommend to the American population.'

Cameron had a brief, private meeting with the president accompanied just by key aides before the main bilateral meeting began

After lunch Obama met with PM Cameron, Foreign Secretary Philip Hammond, Chancellor George Osborne and Home Secretary Theresa May in Downing Street before holding a press conference with the Prime Minister in the Foreign and Commonwealth Office

Royal Guardsman look out from the Quadrangle of Windsor Castle after President Barack Obama and first lady Michelle Obama arrive

The US President's motorcade (pictured) was spotted turning onto Marylebone Road in London this morning

Obama arrived in London late Thursday evening after two days of talks in Saudi Arabia

The President hugs Brooke Brown Barzun, wife of American Ambassador Matthew Barzun, left, at Stansted Airport last night

In his own column for The Sun, Boris Johnson wrote: 'For the United States to tell us in the UK that we must surrender control of so much of our democracy is a breathtaking example of the principle of do as I say, not as I do.

And speaking on BBC's Question Time last night, former UK Defence Secretary Liam Fox said: 'I don't like being told we should accept one thing the Americans wouldn't.'

Mr. Raab, Britain's human rights minister and a prominent Vote Leave campaigner, told the Today show this morning: 'The argument to leave the EU is about having confidence in this country’s future. Can Britain do better outside the EU? I would have to quote Mr. Obama in saying, “Yes we can”.

‘The EU and US free trade agreement has stalled because the EU is not willing to break down barriers to trade. If Britain was outside the EU we would have a far better position to negotiate such deals.'

The President was joined in London today First Lady Michelle Obama and they lunched with Queen Elizabeth II - a day after her 90th birthday.

The White House said this week that Obama has 'come away with an even deeper personal affection' for the Queen every time he meets her.

'She is an important symbol of a country with whom the United States has a special relationship. But she also is a human being whose charisma and a sense of nobility and honor that is something that I think people around the world are attracted to,' White House Press Secretary Josh Earnest said.

Earnest said Obama was 'looking forward' to the lunch.

The president and first lady will also attend a dinner hosted by Prince William, his wife, Kate, and Prince Harry at Kensington Palace.

The Beast was pictured on the streets of London this morning as President Obama made his way to Windsor Castle to meet the Queen

Close up of the US Presidential Cadillac standing in the quadrangle of Windsor Castle, after the arrival by helicopter of the President and First Lady of the United States, Barack Obama and his wife Michelle

The president will be joined in London by First Lady Michelle Obama and they will have lunch Friday with Queen Elizabeth II - a day after her 90th birthday

OBAMA WILL MEET FOUR OF DAVID CAMERON'S TOP MINISTERS - BUT NONE OF THEM BACK BREXIT Barack Obama has met David Cameron and his senior ministers in Downing Street before, five years ago in 2011. Today he will face senior ministers - all of whom support the EU Barack Obama will meet top British ministers in the Downing Street Cabinet Room today but none of them will disagree with his EU referendum intervention referendum. Despite the Government and Conservative Party in Britian being deeply split over Brexit, all the senior ministers invited by David Cameron to take part in the hour-long bilateral meeting back continued EU membership. On the guest list are all the holders of the so-called 'great offices of state' with Chancellor George Osborne, Home Secretary Theresa May, Foreign Secretary Philip Hammond and Defence Secretary Philip Hammond. Not expected to be at the meeting are Northern Ireland Secretary Theresa Villiers - who might be expected to raise the continued support of the US for the peace process - or Justice Secretary Michael Gove, who has responsibility for some aspects of international justice policy. Cameron will also have a brief, private meeting with the president accompanied just by key aides before the main bilateral meeting begins. Topics expected to be under discussion include the battle against ISIS in Iraq and Syria, the continued instability in Libya and the migration crisis in Europe. The two leaders will continue their talks at a meeting of the G5 group in Germany on Monday when they meet wtih German Chancellor Angela Merkel, French President Francois Hollande and Italian Premier Matteo Renzi. Advertisement

Marine One lands as US President Barack Obama arrives at Winfield House, the U.S. Ambassador's residence, where he is staying in London

US Secret Service agents watch on as the president and his entourage walk into into Winfield House, the U.S. Ambassador's residence, following a quick helicopter flight from Stansted Airport

Air Force One touched down at Stansted Airport shortly after 9.30pm local time on Thursday after visiting Saudi Arabia, where Obama held talks with King Salman.

Upon arriving, the president waved as he exited the plane before being greeted on the tarmac.

He was then ushered into the presidential helicopter Marine One before being taken from the airport to the U.S. ambassador's residence.

Police were seen increasing security in and around the airport throughout the day.

Armed officers were stationed around the terminal and outer fencing to ensure the president touchdown safely.