Gordon Brown addressed a range of issues, including old-style bankers' bonuses
Gordon Brown has hit back at claims by Chancellor Alistair Darling that Labour has "lost the will to live".
The prime minister defended his leadership and vowed to "fight for the future", telling BBC One's Andrew Marr programme: "I do not roll over."
He also said laws to "ban" old-style bank bonuses and punish banks who still pay them would be produced shortly.
Ahead of Labour's conference, he denied rumours about his health and insisted his eyesight is not "deteriorating".
Speaking as party members gathered in Brighton for its annual conference, Mr Brown said the country was emerging from the recession because of the actions the government had taken but he now had to "prove we are fighting for the future as well".
He said he would use his conference speech to set out how he would deal with "the whole future of our economy and the whole future of our society".
Asked if the party had "lost the will to live", as Mr Darling has claimed in a Sunday newspaper, he said: "Not at all."
He added: "A setback can either be a challenge that means it's an opportunity to do something better or you roll over. I do not roll over.
"The setback for me is the challenge, the opportunity, to learn of course if you make mistakes and to do things better."
On bankers' bonuses, he promised legislation in the forthcoming Queen's Speech to "ban" the existing system.
It's either yes or no - you either want to have a television debate or you don't want a television debate
He was also asked, for the first time in a television interview, about Westminster rumours he might use concerns about his health as a reason for stepping down as prime minister ahead of a general election.
Mr Marr told Mr Brown he wanted to ask about "something everybody has been talking about in the Westminster village... A lot of people in this country use prescription painkillers and pills to help them get through. Are you one of them?"
The prime minister replied: "No. I think this is the sort of questioning which is all too often entering the lexicon of British politics."
And he denied his sight is deteriorating - something he was asked about last week on US television.
Mr Brown lost the sight in one eye in a rugby accident as a teenager and suffers reduced vision in the other eye, but he said he had recently undergone an annual check-up which showed no deterioration in the vision of his good eye.
When Andrew Marr asked again about the issue of painkiller use, Mr Brown said: "I've already answered that question."
At a conference fringe meeting Lord Mandelson criticised the "degree of personal intrusiveness" in the interview and said he did not have "the foggiest idea" what Andrew Marr had been talking about.
Alastair Campbell, Labour's former director of communications and strategy, told BBC Radio 5 live: "I think people were genuinely really quite shocked that Andrew Marr, on a mainstream BBC programme, sees it as his job now to float rumours that are flying round the internet."
In his message to delegates, Mr Brown said the party went into the conference "clearly as the underdogs" and said they were in for "the fight of our lives".
Gordon Brown: ''Let's win the fight''
He told the audience: "We will not win every seat in the general election - but we will win many that people think we will not win."
He said Labour members should be "angry and determined to fight" the Conservatives: "This is a battle about the future... it's about the future of our country ... It's a fight for our values and a fight for the British people's values. Let's win that fight."
In an interview in the Observer, Mr Darling accuses Labour - from the prime minister and himself down - of appearing to concede the advantage to the Conservatives without a fight.
Likening the party to a losing football side who have allowed their heads to drop well before the final whistle, he says: "We don't look as if we have got fire in our bellies."
Welsh Secretary Peter Hain also warned in an interview with the Sunday Times: "The worst-case scenario is a really bad defeat. We have got to start fighting to win, instead of keeping our heads down heading for defeat.
"If we do that and we lift our heads up, stand tall and start campaigning actively and putting our argument on the doorstep, then I believe the election is winnable. It will be very tough."
The debate comes as an ICM poll for the News of the World found more than half of those surveyed still thought Labour could win the next election under Mr Brown.
Some 11% of the 1,003 adults polled said Labour had a good chance of winning with Mr Brown and 48% said it had a slim chance.
But 41% thought it probably or definitely had no chance, the poll found.
Conservative leader David Cameron, meanwhile, has repeated his call for a televised debate at the election, urging Mr Brown to "get off the fence".
He told Sky News: "It's either yes or no - you either want to have a television debate or you don't want a television debate.
"I do want one. I think it would be good for our democracy, good for our politics and good for the general election, so I hope Gordon Brown will this week make a decision on this."
Asked at a conference fringe meeting whether Mr Brown was the right man to lead Labour, Foreign Secretary David Miliband insisted the prime minister "will prove people wrong" by showing "his resilience and innovation".
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