Tony Blair will return regularly during the general election campaign to bolster Labour efforts to hang on to crucial "Middle England" swing voters, party sources confirmed last night.
Old enmities were buried yesterday as the former Prime Minister poured praise on Gordon Brown's "experience, judgement and boldness" during the financial crisis.
Despite the legacy of the Iraq war and resentment over Mr Blair's post-Downing Street earnings, Labour strategists are convinced he remains popular among former Conservative supporters won over by the party in 1997.
They are pencilling in more "strategic interventions" by Mr Blair in the run-up to polling on 6 May. His task will be to demolish suggestions that David Cameron is the "heir to Blair" and to argue that Labour retains its reforming zeal under his successor.
A heavily tanned Mr Blair chose his former constituency of Trimdon in County Durham for his first intervention in domestic politics since his resignation in 2007.
He received two standing ovations as he tore into Mr Cameron's "time for a change" message as the "most vacuous slogan in politics", claiming the Tories had yet to set out a coherent platform.
He also argued that New Labour had spelt out the detailed policies it would implement in government during the run-up to the 1997 election.
He claimed that, by contrast, the question marks over the Tories' position had intensified, adding: "They look like they are either the old Tory Party, but want to hide it, or they're not certain which way to go."
Mr Blair maintained that Mr Brown had taken all the right decisions at the onset of the credit crunch, helping Britain to emerge "better virtually than any predicted".
He said: "At the moment of peril, the world acted, Britain acted. The decision to act required experience, judgement and boldness. It required leadership. Gordon Brown supplied it."
During a question and answer session with the party faithful, from which the press was excluded, Mr Blair disclosed that he employed some 130 people through his various charitable foundations.
After the event, Father John Caden, who baptised Mr Blair's children, said: "It was typical Tony, and a brilliant speech. He certainly rolled back the years."
Derrick Brown, a retired trade union official, said: "He has recharged our batteries. There's quite a few in the party who are not happy about the Iraq war, but I don't think he is a liability."
A Labour source told The Independent last night: "We expect all our key players, including Tony Blair, to play a full part in the election campaign."
A source close to Mr Blair said his role as Middle East peace envoy took up much of his time, but added: "He will also be making time for the campaign. Over the last two-and-a-half years he hasn't been involved in UK politics, but he thought it was time to do so as attention was turning to the election. He will do whatever Gordon wants him to do during the campaign."
Yesterday the debate raged over whether Mr Blair's return would help or hinder the party he once led. Mr Brown said: "I welcome him saying there is a real risk, a real danger, a real threat from the Conservative Party."
David Hill, the former Downing Street director of communications, said Mr Blair would "appeal to many of those marginal voters who are very important in what is obviously going to be a very close election".
But Mr Cameron insisted he was not worried about Mr Blair's entry to the campaign, saying: "It is nice to see him making a speech no one is paying for."
The Conservatives also called for an investigation into the extensive business interests he has accumulated since stepping down. Greg Hands, the shadow Treasury minister, said Mr Blair appeared not to have registered Windrush Ventures, a company he set up in 2007, with the body that vets former ministers' business activities.
The Labour former minister Peter Kilfoyle warned that Mr Blair's return to the fray would cost the party votes.
"He evokes very strong antagonism, frankly, particularly because of the Iraq war, but not only that – I think he epitomises all that people see as wrong about New Labour," Mr Kilfoyle said.