'Big four' united as they press for labour-friendly legislation

While the political venom is ostensibly aimed at Mr Blair, conference delegates will also be seeking to set down a marker for the Chancellor of the Exchequer, Gordon Brown, who is expected to succeed him and will be addressing the conference today.

The main flashpoint is likely to be a motion by Tony Woodley, leader of the Transport & General Workers' Union , who said today's debate on union freedoms would constitute a "defining moment'' for Labour.

Referring to the bitter Gate Gourmet dispute at Heathrow, Mr Woodley said: "Our party has to choose between some of the most restrictive employment laws in Europe, which allowed decent men and women to be sacked, or to be the party which at long last stands up for the weak and vulnerable.''

Mr Woodley said he was disgusted that a Labour government had refused to condemn an employer who had "locked up middle-aged Asian women in a canteen'' and had flown in labour from abroad to replace the workers it had sacked.

It is understood that the T&G resisted approaches from officials at No 10 urging the union to withdraw its invitation for workers from the catering company to lobby the conference.

Emissaries from Downing Street were trying last night to tone down the resolution, but the thrust of it is expected to remain intact.

The motion tabled by the T&G urges ministers to introduce a law which would stop employers taking on an alternative workforce to replace strikers, simplify procedures governing ballots on industrial action, and allow solidarity stoppages where there is a "close connection'' with the workers in dispute. Baggage handlers at British Airways, Gate Gourmet's main customer, went out on strike in sympathy with the hundreds of staff who were dismissed.

Another motion, tabled by the GMB general union, expected to be passed today, will urge the Government to force employers to make contributions to employees' pensions, demand that public servants be allowed to continue to retire at 60, and call for ministers to tie state pensions to average earnings.

Derek Simpson, general secretary of Amicus, the biggest single donor to the Labour Party, will propose a resolution calling on ministers to harmonise British employment law with legislation on the Continent offering greater protection against redundancy.

The "big four'' unions - Amicus, the T&G, the GMB and Unison - have all agreed to back each other's motions, which guarantees 40 per cent of the conference vote.

On Wednesday the public service union Unison will demand a halt to the privatisation of public services. The Prime Minister insisted yesterday that the aim of his reforms was to make state health and education services so good that no one needed to "go private''.