London: British Prime Minister David Cameron has called Jean-Claude Juncker to congratulate the man he tried to block from becoming European Commission president.

Mr Cameron's failure to prevent Mr Juncker getting the job after a bitter campaign was seen as a blow to the premier that could increase the likelihood of Britain leaving the European Union.

British Prime Minister David Cameron. Credit:AFP

A spokesman for the British Prime Minister said Mr Cameron had phoned to congratulate Mr Juncker on his successful campaign, and on securing the nomination.

"They discussed how they would work together to make the EU more competitive and more flexible," the spokesman said.