A Cabinet committee is expected this week to agree the final detail of the controversial Fairness at Work Bill included in the Queen's Speech.
Mr Mandelson has gone a long way to meeting the demands of unions against the wishes of employers' organisations, but officers of the backbench trade union committee of Labour MPs who met Mr Mandelson last week are planning to table a Commons motion seeking further concessions.
Unions will be expected to meet a 50 per cent threshold in ballots before demanding recognition by employers and Mr Mandelson has dropped a proposal requiring those taking part in ballots to have been members of unions for at least three months. But the MPs are unhappy that the Central Arbitration Committee will be given wide powers under Mr Mandelson's Bill to assess claims for automatic bargaining rights. They want its terms of reference to be tightly limited by the Bill.
"There is a lot of concern about the flexibility which Mr Mandelson is proposing," said a senior member of the Labour backbench group.
More than 70 MPs attended a meeting of Labour's backbench trade union committee to hear John Monks, the general secretary of the TUC, express his concern at the compromise being worked out by Mr Mandelson over the fair employment legislation.
"John Monks was given a good reception, but Peter Mandelson was not," said one senior Labour backbencher. "There is going to be a row over this."
The rumblings of backbench discontent emerged after Mr Mandelson sought to reassure the MPs that the principles underpinning the White Paper on trade union recognition were being protected. But many MPs emerged from the meeting seeking stronger assurances that the Secretary of State is not ready to bow too much to the bosses.
Gerry Sutcliffe, Labour MP for Bradford South and chairman of the group, said the Commons motion which he will be tabling with senior backbench colleagues would welcome the Fairness at Work legislation but would urge the Cabinet to adhere to the principles in the White Paper on trade union recognition.
The MPs left the meeting with the firm view that many details of the legislation remain to be settled, and a Cabinet battle could be about to begin. They believe that John Prescott, the Deputy Prime Minister, has been given assurances by Tony Blair that he will be involved in the final decisions, which the MPs regard as another reassurance that past pledges will be kept.
In a separate move, Harriet Harman, the former Social Security secretary, will also urge the Government to help fund more generous provisions for parental leave.
In her first moves since being sacked from the Cabinet, she will table a Commons motion today with Chris Pond, the Labour MP and former director of the Low Pay Unit, welcoming government action but making it clear that they want to see more financial help for parents taking leave to care for their children.Reuse content