The so-called union "barons" said they regarded the new decision-making structure, likely to be endorsed next week at the party conference, as a "settlement" and would oppose further reforms.
The strictures from unions, which still hold half the decision-making votes at the conference, came as delegates gathered in Brighton for the celebratory post-election assembly.
Party leaders were expecting Mr Blair's vision of the party to be endorsed by delegates, but politicians on the left of the party have accused the leadership of manipulating the conference agenda to get the big debate on party reforms over on Monday. The controversial "Partnership in Power" proposals will change Labour's policy-making process, giving such responsibilities to a high-level committee and to a national policy forum.
In an interview with The Independent, the right-wing leader of the Amalgamated Engineering and Electrical Union, declared that the changes to party decision- making processes set out in "Partnership in Power" had gone far enough.
Ken Jackson, general secretary of the AEEU, said bluntly:"It's our party, we founded it and we still fund it. The leadership has needed us in the past and will continue to need us."
Referring to a step-by-step erosion of unions' power over the party, Mr Jackson said: "Our share of conference votes has gone down from more than 90 per cent to 50 per cent and there it must remain."It is known that privately Mr Blair would like to see it decline further.
The warning comes from a union which has traditionally backed the modernisers in the party, but the AEEU has become increasingly disenchanted with the leadership's attitude to the main financial backers.
"We at the AEEU must have given them the equivalent of pounds 18m during the Tory years. The unions in total must have provided the party with a sum in excess of pounds 100m," he said.
As disclosed in The Independent, the AEEU withheld pounds 250,000 in election funding from the party in protest at the leadership's insistence on "parachuting in" middle-class parliamentary candidates at the expense of working people.
Roger Lyons, leader of the MSF manufacturing union, said there should be no more reforms of the party decision-making process in this Parliament. "We are not saying that things will never change again. But we want to retain the federal nature of the party. I know that nearly all of the major union leaders concur."
Monday evening will see the result of Peter Mandelson's bid for a seat on the Party's National Executive Committee (NEC), and it has been suggested that a disappointment for him might affect the Party's mood on reforms with which he has been associated.Reuse content