Lord Desai on the future of Gordon Brown's leadership
Labour's "only hope" of winning the next election is a "changed, improved" Gordon Brown, a senior Labour peer has told the BBC.
If he cannot change, Lord Desai said, the prime minister should be asked to "move over" for the sake of the party.
But former deputy prime minister John Prescott defended Mr Brown, saying he was the "one man in our whole system" who could solve Britain's problems.
"Let's have a bit of trust. Gordon can do the job," Mr Prescott said.
"Let's get behind him - nobody's got any appetite for replacing [him]."
Mr Prescott was speaking as pressure mounted on the prime minister following Labour's crushing defeat in the Crewe and Nantwich by-election.
He told BBC Radio 5 Live: "This man has got a record to show how he can improve it [the country].
Gordon Brown is our only leader and we have to either win with him or lose with him
Lord Desai, Labour peer
"I want that man at the helm, who knows what the problems are, has shown he's done it over the last 10 years and if he doesn't smile too much, so what, judge him on his record."
Mr Prescott's support came after he described Mr Brown as "annoying and prickly" in his recent autobiography.
Earlier, his successor, the current deputy Labour leader Harriet Harman, said the vast majority of Labour members were "solidly behind" Mr Brown.
But former foreign secretary Margaret Beckett said Mr Brown must learn from the electorate's "clear desire to see a change of course".
Lord Desai, a leading economist, said there was "no choice for the Labour party except to live with Gordon Brown".
"He should say to the party, 'Put up or shut up. I am your leader, if anybody wants to challenge me, here I am, try it.'
"Nobody's going to do it and that will establish his authority."
Lord Desai said that, although change would not be easy, there was still hope: "I know he has difficulty changing his style, he's set in his ways, but we can recover because, policy-wise, Gordon Brown still has good ideas.
"Gordon Brown is our only leader and we have to either win with him or lose with him."
But the peer said if Mr Brown did not respond to criticism, Justice Secretary Jack Straw should take his place.
Jack doesn't think this is the time for a leadership challenge
Spokesman for Justice Secretary Jack Straw
"Either we require a changed, improved Gordon Brown to lead us, and we still hope for that, or somebody has to say, 'Please for the sake of the party that you love, move over', but I don't think it's going to happen."
A spokesman for Mr Straw said the Crewe by-election result was a message "for all of the party, not just Gordon".
"Jack doesn't think this is the time for a leadership challenge. Everyone in cabinet is just getting on with the job."
Michael Meacher, the former environment minister who tried to contest Gordon Brown for leadership of the Labour party last year, says it was time for a radical change in direction.
He told the BBC: "I think new Labour is dead - I think the policies which have been pursued have not sufficiently represented those that the Labour party has always represented.
"Of course we need the middle ground - that is one thing that new Labour certainly emphasised in its early years and I totally accept that - you can't win an election just on your core vote.
"But you do have to ensure that that core vote is satisfied and is backing you."
We've got to find out what's wrong and do something about it.
Austin Mitchell, Labour MP for Grimsby
Austin Mitchell, Labour MP for Grimsby, told BBC Radio 4 that there was no point in changing leader, but Mr Brown must learn to listen more.
"We've never actually listened and, to be fair, Gordon hasn't listened to us," he said.
"Well, now we've got to listen and we've got to find out what's wrong and do something about it."
Labour MP Phyllis Starkey said: "I certainly don't think that if we revert into an internal party dispute that we're going to increase our standing with the electorate.
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