The Prime Minister has agreed to meet TUC leaders again, in advance of publication of a White Paper, "Fairness at Work", which is due out soon following protracted negotiations between both sides of industry.
In the meantime, the unions will also hold talks with Margaret Beckett, President of the Board of Trade, whose department is responsible for drawing up the legislation.
Relations between the unions and Downing Street cooled sharply last week after a meeting between the Prime Minister and TUC leaders. The unions believe Mr Blair is preparing to come down on the side of the CBI in a long-running argument over recognition in the workplace.
Bill Morris, general secretary of the Transport and General Workers' Union, proposed an emergency Trades Union Congress to lay down the labour movement's line on the White Paper. His proposal has been backed by the engineering workers and the train drivers, but other big unions - notably Unison and the GMB - are reluctant to throw their weight behind the initiative.
TUC leaders originally agreed to maintain silence over the talks with Mr Blair, but amid misgivings about the Government's intention, the TGWU decided to raise the unions' game. Mr Morris insisted: "This is a fundamental issue for the future of workers' rights in this country, and judgement on it should be made by the full TUC."
John Monks, TUC general secretary, who has called an advisory conference of all 75 affiliated unions for 6 May, opposes the idea. "I am still confident that the TUC's arguments will win the day," he said. "I am looking forward to a White Paper in line with Labour's manifesto."
The manifesto promised that where a majority of workers voted in a ballot for representation by a trade union, the law would provide for recognition. But employers say this should be interpreted as a majority of all those entitled to vote, rather than those actually voting, and union leaders fear that in their honeymoon with business, ministers will cave in to that demand.
The TUC has pointed out that if this were the test of electability, only 16 Labour MPs would have been returned to parliament last May.
The unions are also furious about CBI proposals to end the immunity from legal action for industrial action in support of a claim for recognition, and to impose a three-year "cooling off" period before unions could come back after a ballot that does not achieve a majority. They also claim that provisions for de-recognition could make it easier for employers to get rid of unions than it would be for unions to become established.
Legislation on this controversial issue is due to be included in the Queen's Speech in November. The White Paper was due out at the beginning of the year, but as rancour over its contents mounted, the timetable has slipped.Reuse content