British prime minister David Cameron’s bid to reform the EU is doomed and presents the “biggest threat” to Britain’s future prosperity, Ed Miliband has warned.

The Labour leader said Mr Cameron's strategy had already failed because fellow European leaders were not listening to him.

In a Labour Party conference speech, Mr Miliband highlighted Mr Cameron's unsuccessful effort to block Jean-Claude Juncker's appointment as president of the European Commission.

The UK was eventually outvoted on the issue by 26 nations to two. "The problem for our country is when David Cameron comes calling people don't think he's calling about the problems of Britain or the problems of Europe, " Mr Miliband said.

"They think he is calling about the problems of the Conservative Party. "And if you are elected the chancellor of Germany, or the prime minister of Italy, or the president of France, you don't really think you were elected to solve the problems of the Conservative Party."

“That’s why he can’t succeed for our country. What we had over Jean-Claude Juncker is just a preview of what could befall this country if David Cameron were back in power after 2015.”

“He has to win 28-0 to get reform of Europe. No chance for David Cameron. He’s got no chance of fighting for this country because people think he has got one hand on the exit door. His strategy has failed.”

“If you want to reform Europe, if you want to change the way Europe works, if you want to keep Britain in the EU and you realise that the biggest threat to our prosperity is the Conservative Party, then the answer is a Labour government.”