Labour is plotting to join forces with Tory rebels in an attempt to sabotage the Government's plans for House of Lords reform before the proposals are even debated.
Nick Clegg is expected to publish his Lords Reform Bill on Wednesday after agreeing a series of concessions with David Cameron in an attempt to win over Conservative MPs.
However, in a strategy designed to exploit the divisions within the Coalition, Labour will use a Commons procedural motion in an attempt to derail the bill at its first hurdle.
They are expected to vote against a Commons timetable for the Bill – forcing every part of it to be debated by the whole house rather than in committee.
Such a move would also mean ministers would lose the power to limit debate on the Bill by imposing "guillotine" motions. Final details of the Lord Reform Bill are expected to be agreed by a full meeting of the Cabinet on Tuesday and will go before the House before the start of the Parliamentary recess next month.
In an attempt to win over Tory rebels, Mr Cameron and Mr Clegg are believed to have agreed the Bill should include a clause explicitly spelling out the primacy of the House of Commons and a guarantee that elections to the new-look House of Lords would not take place on current parliamentary constituency boundaries.
Both were key concerns of Conservative backbenchers who feared an elected House of Lords might challenge the Commons for supremacy and be used as a way of undermining constituency MPs. But it still may not be enough to head off a rebellion by up to 80 Tory backbenchers who, in part, see the legislation as a way of taking revenge on the Lib Dems.
They are angry in particular that Liberal Democrat MPs failed to back the Culture Secretary, Jeremy Hunt, in the row about the BSkyB take-over as well as the Liberal Democrat's opposition to plans to abolish GCSEs. Some Tory backbenchers see defeating Mr Clegg's legislation as "payback".
Yesterday it was reported that up to five Parliamentary Private Secretaries (PPS), who act as unpaid aides to Ministers could resign rather than vote for the Government on the issue.
These include Conor Burns, who works for Northern Ireland Secretary Owen Paterson, Angie Bray, PPS to Cabinet Office Minister Francis Maude, and Mark Menzies, PPS to Energy Minister Charles Hendry.
The legislation is expected to propose cutting the number of lords from about 900 to 300, with at least 80 per cent of peers being elected.
Mr Clegg is expected to lead the first Commons debate on the Bill in the second week of July.