James Purnell has been tipped as a future Labour leader
Cabinet minister James Purnell has refused to condemn Labour's rebel MPs and warned there is no "magic bullet" to win back voters.
He told the New Statesman all parties had been slow to respond to economic turbulence and people had "slightly turned away from us".
One minister has quit and 12 Labour MPs have called for a leadership challenge.
Mr Purnell said he did not agree with them but it was "ridiculous" to pretend MPs could not complain when worried.
In his interview, the Work and Pensions Secretary, who has been talked of as a future Labour leader himself, told the magazine the changing economic circumstances had wrongfooted all parties.
"Something happened earlier in the year when we were pursuing the policies which were very much based on the old political challenges," he said.
"That's why people slightly turned away from us and there's no magic bullet to put that right, actually."
He said he agreed with his colleague, Business Secretary John Hutton's refusal to condemn the rebels adding: "I think it would be ridiculous to pretend that you can't complain when you're worried.
"I mean, I'm worried that we're 20 points behind. I'm not going to condemn people or question their motives. [But] I don't agree with what they did."
Asked whether he would support a future leadership challenge, he replied: "One of the great wisdoms of politics is not to answer hypothetical questions and that's a hypothetical question. As John [Hutton] said, the job of the cabinet is to support the Prime Minister and that's what we're going to do."
Pressure has been mounting on Mr Brown after Scotland Office minister David Cairns resigned on Tuesday, and 12 other Labour MPs requested nomination forms for a leadership challenge.
Meanwhile the BBC understands that Eric Joyce, a ministerial aide to the Business Secretary John Hutton who has been reported to be considering resigning, has told Downing Street he is remaining in his job through the party conference and the Glenrothes by-election.
George Howarth, one of the rebels calling for a contest, said of Mr Brown: "He's so unpopular that no one can remember a time since Neville Chamberlain, after Hitler invaded Norway, that anyone was so unpopular."
He said that the timing of the revolt against the prime minister was "in many ways appalling" but said that "wasn't of our making".
"I didn't leak the letters that said we wanted a leadership contest. Others who did that may have to answer for their actions at some point in the future," he said.
Asked about the comments later, the prime minister's spokesman said: "The PM is not giving these matters a moment's thought. What he is concerned about is dealing with the big issues facing the country."
Meanwhile Mr Cairns' former boss, Scottish Secretary Des Browne, has warned potential Labour rebels there is no alternative to Mr Brown's leadership.
Mr Browne, who is also the defence secretary, said Labour's conference, which begins in Manchester at the weekend, would provide an opportunity to persuade voters it had the right policies for running the country.
He told the BBC's Good Morning Scotland he "deeply regretted" Mr Cairns' departure but insisted he was wrong about Gordon Brown, saying the prime minister was the best qualified to lead the country through difficult economic times.
"While it is undoubtedly the case that people have other views, the party's position is that we should support our prime minister in government," said Mr Browne.
The BBC's political editor Nick Robinson, said calls for a leadership contest were being echoed, in private, up to cabinet level and there were some cabinet ministers who believed Mr Brown had to go.
But he added there was a big difference between talk and action and Mr Brown could survive as long as no major figure stood against him.