David Miliband insists he does not want a leadership challenge
Foreign Secretary David Miliband has thrown his support behind the prime minister and rejected calls for a Labour leadership contest.
Mr Miliband told BBC One's Politics Show he believed Gordon Brown was fully capable of winning the next election.
However cabinet colleague John Hutton said he would not criticise Labour MPs who called for a leadership contest.
He also refused to criticise those who wanted Labour "to set out a stronger vision of what we are doing".
But Mr Hutton, the Business Secretary, also said he did support Mr Brown "because he is setting the right direction for Britain".
He told the BBC: "It is right and proper in a democracy that there should be that debate, within the Labour movement, within the Labour party at the moment about our future direction.
"I'm not going to criticise any of my colleagues who want Labour to do better and neither am I going to criticise those who say, for example, that we do need to set out a stronger vision of what we are doing.
I think we should give someone else a chance to take over
"It is a difficult political climate for us. There is no question at all about that.
"So I think my colleagues are right to say that the government need to do better. For heaven's sake, we are 20 percentage points behind in the opinion polls.
"And that is a challenge to all of us in the cabinet to do better - not just to Gordon as prime minister, but to all of us to do better, to make our arguments more convincing and clearer."
Mr Miliband has been tipped as a potential successor to the PM, and his decisiion to speak out against the rebels is seen as particularly significant as he has been seen as a contender for the top job.
He said: "I don't support their (the rebels) argument that we should trigger a leadership contest.
"I've said I expect Gordon to lead us into the next general election. I will support him in doing so."
In July, Mr Miliband wrote an article outlining Labour's future but with no mention of Mr Brown. The move was seen by many as an attempt to test the water over a potential take-over bid.
In response to questioning on the Politics Show, Mr Miliband denied he had "bottled it" at the time by not following through with a challenge.
So far more than a dozen MPs have called for a leadership contest including former Labour minister Fiona Mactaggart and party vice chair Joan Ryan.
She was sacked from her party post after supporting the demands.
It's very difficult to see what they do next
Laura Kuenssberg BBC political correspondent
Meanwhile, according to the Scotsman newspaper, the unrest being caused by some Labour MPs risks wrecking the party's chances in the crucial Glenrothes by-election.
Labour is defending a majority of more than 10,000 in the Westminster seat, left vacant by the death of MP John MacDougall.
According to Jim Devine, MP for Livingston, a recent opinion poll showed 79% of people were put off by Labour because the party was divided.
The latest Labour MP to cal for a challenge to Mr Brown is fomer minister Barry Gardiner, now a special envoy on forestry for the prime minister.
He said: "I was one of those who nominated Gordon last year, and I was very hopeful that he would come in with a very clear vision for the country, and unfortunately I don't think he's managed to do that.
"I think the public have therefore stopped listening to him."
Rally of support
On Friday, junior whip Siobhain McDonagh was also fired for calling for a debate on Gordon Brown's leadership.
John Hutton says the cabinet should rally behind Gordon Brown
Another of those who called for the leadership nomination papers, Labour MP Frank Field, said those calling for a contest had initially done so in private, but he suspected Mr Brown's supporters had leaked the story in order to smoke out the rebels.
He told the BBC: "As far as I know none of us leaked to the media that this attempt was occurring.
"It appears that those close to the centre of government leaked this story in an attempt to smash the efforts to get a gauge of parliamentary opinion.
"And that itself is pretty worrying - that you can't write in private to the Labour party without the letters then being used as an attempt to thwart what I see as a quite legitimate objective."
BBC political correspondent Laura Kuenssberg said the rebels were attempting to lay a trap for Mr Brown, forcing him into a leadership contest.
But she said this was a risky strategy.
"Clearly this has been organised - a drip, drip over the days. But until there's a major figure like David Miliband, or perhaps Alan Johnson, who's willing to take their challenge forward... it's very difficult to see what they do next."
Our correspondent said public in-fighting was always very unpopular with the electorate and that for the Conservatives and the Liberal Democrats, the row was "a dream come true".
However, she added: "This could have the lid put on it in the next couple of weeks."
Other ministers have rallied to support the prime minister, arguing that it is not the time for a challenge to Gordon Brown - nor for a public debate about the future of the party.
The Labour Party has said nine MPs have so far asked for nomination papers to be issued to all members of the parliamentary party - five of these have now made their names public.
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