Gordon Brown has attempted to breathe fire into the belly of Labour activists by telling them: "Let us build the Britain of our dreams."
The prime minister told Labour's spring conference in Birmingham the past few months had not been easy for the party.
But he urged it to work for victory at May's local elections, as only Labour could deliver the change voters wanted.
It was his first speech to the party since his decision not to call a general election in October.
Mr Brown received a standing ovation from delegates for the speech, which avoided big policy announcements in favour of setting out his vision for the future.
He urged activists to "embrace a new age of ambition" and told them a "Britain of security and opportunity for all is within our grasp".
He said only Labour - and not the Conservatives - had the "passion" and commitment to deliver more opportunity.
"Imagine if together we build a Britain where what counts is not how high up you start, but how high you can reach.
"A Britain where every parent of every child born today can watch them as they sleep and dare to believe that nothing is beyond them realising their potential.
"And imagine if together we create a Britain where, for all of us, the future is not a fate we can't escape but a common purpose we create."
But Conservative leader David Cameron, in a speech earlier to the Welsh Tory conference, said people were "fed up with Labour" and only the Conservatives offered a new agenda.
And he accused Mr Brown of helping to destroy public faith in politics with Labour's "systematic culture of spin".
In his Birmingham speech, Mr Brown pledged to rebuild or refurbish more than 320 schools by 2010, ensuring half of GP surgeries are open for at least one evening or weekend session every week by 2009 and building three million more homes.
He also underlined his commitment to eradicating child poverty, describing it as "the scar that demeans Britain".
And he repeated his pledge that every child should leave school able to read, write and count - with personalised tuition if necessary.
He also defended Chancellor Alistair Darling - who has faced calls for his resignation over his handling of the Northern Rock nationalisation - hailing the latest figures showing record numbers in employment and saying full employment was "nearly within our grasp".
He said: "My pledge to the British people is that at all times we will keep inflation and mortgage rates low and ensure stability.
"And with our programme for three million more houses, many of them in eco towns, we will enable thousands more young people to afford to buy a home of their own."
He also responded to calls from his own backbenchers to legislate for equal rights for agency workers and said Labour would honour its 2005 election promise of "stopping good employers being undercut by the bad".
On the environment he hailed Labour's plans for legally binding emissions targets and pledged to "lead the world by example in triumphing over climate change".
He also emphasised his commitment to security - although an expected passage confirming the issuing of ID cards to foreign nationals next year was not included in the final version of the text.
Cabinet Office Minister Ed Miliband earlier acknowledged the government had been through a difficult period but insisted that Labour could go on to win a fourth general election.
Labour is expected to face a tough fight at May's elections, when it will be contesting elections for about 160 councils in England and all Welsh councils.
It also faces a crucial test in London, where Ken Livingstone is running for a third term as mayor.