Prime Minister Gordon Brown has sought to re-establish his authority as Labour leader during his speech to the party conference in Manchester.

Mr Brown acknowledged that he was seen as "too serious" and conceded that the 10p tax debacle had "stung" him.

But he warned the party conference audience: "The British people would not forgive us if at this time we looked inwards to the affairs of just our party when our duty is to the interests of our country."

Mr Brown, who wore a dark suit and a purple tie, received a four-minute standing ovation following his 53-minute speech.

He unveiled plans to scrap prescription charges for cancer patients, promised free universal health checks for everyone over 40 and said he would give elderly people help to stay in their homes and escape the costs of going into care.

But addressing the issue of his image, Mr Brown told delegates: "I didn't come into politics to be a celebrity or thinking I'd always be popular. Perhaps that's just as well."

He added: "I'm not going to try to be something I'm not."

The build-up to Mr Brown's speech - billed as a make-or-break moment - has been dominated by questions about his leadership.

But the Prime Minister said: "I want to give the people of this country an unconditional assurance - no ifs, no buts, no small print - my unwavering focus is on taking this country through the challenging economic circumstances we face and building the fair society of the future."

Mr Brown promised to do "all it takes" to stabilise turbulence in the markets and join other countries in "rebuilding" the world financial system.

Union leaders warmly welcomed Mr Brown's speech and pledged to work with him to try to win Labour a fourth term in office.

Billy Hayes, general secretary of the Communication Workers' Union, said: "This was a very positive speech. With the current global economic crisis he is the right person at the right time."

Derek Simpson, joint leader of the Unite union, said the Prime Minister had scored an "injury time winner" and he predicted that Labour could now go on to win the next election.

The man tipped to take over from Mr Brown Foreign Secretary David Miliband said: "The speech was an excellent speech. I think Gordon found his true voice."

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