John Reid will warn Gordon Brown today that he could lose the next general election if he abandons the New Labour agenda after becoming Prime Minister.
The Home Secretary will join a drive by Blairites to persuade the Chancellor not to distance himself from New Labour's reforms if, as is widely expected, he succeeds Tony Blair this year.
The campaign is irritating allies of Mr Brown, who claim that the Blairites are handing ammunition to the Conservatives by appearing to doubt the Chancellor's credentials.
In a speech to Labour supporters in south London, Mr Reid will argue that Mr Blair's successor would play into Conservative hands by failing to continue Mr Blair's agenda after his resignation.
He will say: "The Tories will try to argue that Tony Blair equals New Labour. They will say that when Tony Blair goes New Labour goes with him. That is not the case and we must show that it is not true. The New Labour project was not the product of one person, nor even a few, but of the efforts and energies of many people over decades.
"Although Tony may be stepping down, the underlying analysis and philosophy of New Labour is one shared by all of us in government and will continue undimmed. New Labour does not and will not start and end with Tony Blair."
Mr Reid has not ruled out standing against Mr Brown for the leadership, although he is thought unlikely to do so. While his speech will be seen as a barely coded warning to the Chancellor, he will also praise Mr Brown's record, saying that it towers above anything to which any Conservative could aspire.
The Home Secretary will say: "We will win or lose the next election by our own hand. That is why it is so important that the electorate understand that we intend to remain New Labour to the core - and that the Labour Party itself understands the importance of doing just that."
Otherwise, he will suggest, the party would allow, by default, the impression to persist that New Labour has been nothing more than Tony Blair.
Mr Reid will argue that New Labour's identification with the ambitions of working people is not an alternative to compassion but goes alongside it. "The essence of New Labour is about letting people know that we are as much on the side of those who were getting on as we are for those who need help, " he will say.Reuse content