He said he was prompted to write a controversial article in a national newspaper because of the sense of "fatalism" in the party after its defeat in the Glasgow East by-election.

Mr Miliband outlined his vision for the Labour party in that article, and that had commentators and party activists speculating that the Foreign Secretary was preparing a bid to mount a challenge to Mr Brown's leadership, but he insists that is not the case.

"Can Gordon lead us into the next election and win? Yes. I'm absolutely confident about that," he said.

He said his article was challenging David Cameron, rather than Mr Brown.

"I'm not campaigning for anything other than a successful Labour government," the Foreign Secretary told a news conference.

"The truth is we had a bad result last week and I was frustrated by the fatalism in the media and in the Labour Party.

"You might insist that personality comes before issue and argument, I don't believe that.

"Does Gordon Brown have values and vision - yes!"

Mr Miliband told a media conference that Mr Brown was the leader of the Labour Party and that "he will lead us forward to address the big issues".

"The next General Election can be about change versus more of the same, with Labour representing change," he said.