In a recent meeting senior union representatives told the Labour leader that their vote at annual conferences should not be cut below 50 per cent.
Unions will wield 70 per cent of the votes at this week's annual party assembly in Brighton, but the proportion is due to move down to half next year.
At the biennial conference of the Transport and General Workers' Union in the summer Mr Blair indicated that he could envisage the percentage being reduced further as individual party membership increased.
However at a meeting of the "contact" group in the Commons, leaders of all the largest Labour affiliates told Mr Blair that they had serious misgivings about his policy of "constant revolution" of the party's internal structure.
Revelations about the contact meeting will be used by the Government to argue that the party is still "in hock" to the unions despite the new Labour image promoted by Mr Blair.
Most worrying for the party leadership was the attitude of the ultra- loyalist and right-led Amalgamated Engineering and Electrical Union, which was among the affiliates counselling caution on any further changes. The AEEU has been the one of the most vociferous supporters of one-member one-vote in the party and the union's leaders have previously said the principle should be extended to policy-making assemblies.
Ken Jackson, acting general secretary of the AEEU, revealed yesterday that Mr Blair had been warned that union voting power should not be reduced below half.
"The trade union movement is united left, right and centre on this issue," said Mr Jackson. "We agreed that 50 per cent should be the floor.
"We believe union members form a fair chunk of the electorate. If they support the Labour Party, they should have a major involvement in policy- making." He said that if unions backed the reduction of the percentage even further they would be acting like "turkeys voting for Christmas". It was important that the interests of working people were represented.
Mr Jackson also said the union disagreed with Mr Blair's over the sponsorship of MPs. The Labour executive is consulting members over a plan to channel financial backing from unions to constituencies rather than individual MPs.Reuse content