Barack Obama has called on Britain to remain in the European Union.

In an interview last night, Barack Obama said the EU has "made the world safer and more prosperous" as "part of the cornerstone of institutions built after world war two that has made the world safer and more prosperous".

He also said British Prime Minister David Cameron has been "an outstanding partner" and congratulated his government on meeting the Nato target of spending two per cent of GDP on defence.

Speaking to the BBC, President Obama said having Britain in the EU helps make the world safer and gives the United States "much greater confidence about the strength of the transatlantic union".