President Obama delivering the 2015 State of the Union address. Image - White House/Pete Souza President Obama delivering the 2015 State of the Union address. Image - White House/Pete Souza

US President Barack Obama has called on the British public to "stick together" with the European Union in June's crucial referendum.

Arriving in the UK to celebrate the Queen's 90th birthday, Mr Obama penned an article in The Telegraph, saying: “As citizens of the United Kingdom take stock of their relationship with the EU, you should be proud that the EU has helped spread British values and practices – democracy, the rule of law, open markets – across the continent and to its periphery."

Knowing that criticism would inevitably come from 'Leave' campaigners, the President stressed that the outcome of the referendum is "a matter of deep interest to the United States".

He said: “I am persuaded that the greatest single contribution our two countries have been enabled to make to civilisation, and to the welfare of peoples throughout the world, is the example we have jointly set by our manner of conducting relations between our two nations.”

Many leave campaigners have suggested that severing ties with the EU would allow the UK to forge even closer relationships with the US. But Mr Obama appeared to quash that idea: “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.”

The US sees how your powerful voice in Europe ensures that Europe takes a strong stance in the world, and keeps the EU open, outward-looking, and closely linked to its allies on the other side of the Atlantic. So the US and the world need your outsized influence to continue – including within Europe.”