In a warning directed at Alan Milburn, who has supplanted him as the party's chief election strategist, the Chancellor said he would ensure that Labour maintained its fiscal discipline over the next few years.
Allies of Mr Brown fear that Tony Blair and Mr Milburn will press for a new wave of public service reforms in the manifesto which are not properly costed or thought out.
Addressing a Treasury conference on volunteering, Mr Brown insisted: "In the coming few years our public spending discipline will not waver. We will meet and continue to meet our fiscal rules. There will be no relaxation of that discipline in our election manifesto. Priorities will be rigorously selected and pursued. And there will be no short cuts or easy options adopted in the maintenance of fiscal prudence."
His remarks were seen by Labour MPs as a declaration that he intends to play a pivotal role in drawing up Labour's manifesto, even though Mr Blair has installed Mr Milburn as the party's election and policy co- ordinator.
Mr Brown wants to ensure that any new pledges can be afforded under the three-year public spending blueprint he set out last summer. He is also wary of "gimmicks" such as Mr Blair's plan to cut child benefit for the parents of persistent truants, which was blocked after a cabinet revolt led by Mr Brown.
MPs viewed his comments as a sign of the underlying tensions between the Prime Minister and Chancellor despite the truce they agreed last month after a book claimed that Mr Brown had told Mr Blair he would never trust him again because he reneged on a promise to stand down last year.
The Blair camp kept up its demands for radical reform yesterday when John Reid, the Health Secretary, launched a pamphlet saying that modernisers should not allow themselves to be portrayed as "privatisers" because they backed "choice" in public services. Mr Reid said: "We can learn from market-based systems without being engulfed by them. We can retain our values while improving the manner in which they are translated into contemporary relevance.''
He added: "To those who have misgivings about it, I say I will protect the founding principles of the NHS of equal access to health care provided free at the point of need."
Lord Kinnock of Bedwellty, the former Labour leader who took his seat in the House of Lords yesterday, urged aides to Mr Blair and Mr Brown to stop squabbling. He told the ePolitix.com website: "What people working around them have got to do is just shut up, pipe down, and understand there is no issue, no matter how large it looms in their personal existence, that begins to be worth inflicting damage in the interest of the Labour Party."
In his speech, Mr Brown issued "a call to service" for young people to get involved in voluntary community work.
Steve Richards, page 29