In an interview transmitted by the BBC on Thursday, Obama said the EU had made the world "safer and more prosperous" and that the UK risked losing its global influence if it left the 28 nation bloc.
The president also said that UK membership of the EU gave the US “much greater confidence about the strength of the transatlantic union”.
Obama's comments triggered a lively reaction with British Conservative MEP Daniel Hannan tweeting to his followers: “I accept that there may be some arguments for staying in the EU. Humouring Barack Obama is not one of them."
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The European Conservatives and Reformists Group (ECR) group deputy added in a follow up tweet, "Tell you what, Barack Obama, if you're so keen on the EU, why don't you pay to bail out the wretched euro?
Eurosceptic UK Independence Party (UKIP) MEP Patrick O’Flynn was more indignant, saying Obama was, "unwise to pressurise Britain to stay in the EU for America's convenience," adding, "We need to look to our own national interest first."
However, the president's comments drew the most ire from British MP John Redwood , the darling of the eurosceptic wing of the British conservative party, who said, "If letting foreign countries impose laws on you, levy taxes on you, and spend your money is such a good idea why doesn’t [Obama] create an American Union so Mexico can have common borders with the US, Cuba can spend US tax on herself, and Brazil can impose laws on the US the US does not want”.