David Miliband is “waiting for his brother Ed to fail” as British Labour leader and is “poised” to make another bid for the job, friends of the former Foreign Secretary revealed.

Ed Miliband, who pipped his brother to the post last September, is faced with growing discontent from Labour MPs over his failure to set out a clear strategy and narrative. A poll in the Sunday Times shows more than two in five Labour supporters believe electing Ed Miliband was the wrong decision. The paper also claims “big beasts”, including Lord John Prescott and David Blunkett, are beginning to express unease about his performance.

The head of Britain’s biggest public sector union, Dave Prentis, who backed Ed Miliband in the contest, has also rounded on the Labour leadership for failing to stand up for the national health service.

A friend of David Miliband told the Independent on Sunday that relations are very poor.

The friend said: “David definitely wants it still. He is waiting for Ed to fail. He thinks the coalition will go the full term, so Ed has plenty of time to fail.”

There is no suggestion of David Miliband’s planning a direct challenge to his brother, but his aides are mobilising in the expectation of his brother losing the party’s support.

There was discomfort among Ed allies when the speech David Miliband would have made to the party, had he won, was leaked to the Guardian, in what was described as a “highly provocative act” by Labour insiders.

The leak, an apparent attempt to show MPs what “might have been”, seemed to come from someone close to the former Foreign Secretary.