Jeremy Corbyn has accused ministers of an “unprecedented attempt to rig Parliament”.
The Labour leader accused Theresa May of trying to “grab power” with “no majority and no mandate” by stacking key committees with Tory MPs.
The political composition of committees which scrutinise legislation usually reflects that of the Commons.
But the government’s plans would give it a majority on them – despite losing its majority in the general election.
Downing Street has defended the move, first revealed by the Huffington Post, saying: “These proposals create the fairest balance between the opposition and government, and will ensure technical, procedural rules do not cause unwarranted delays to the business of Parliament.
“The adjustments provide for maximum scrutiny with minimum disruption and delay, both to parliamentary proceedings and to the governance of the country.”
But Labour MPs joined their leader in condemning the proposals. Ben Bradshaw tweeted: “May thinks she’s a dictator. Outrageous.” Valerie Vaz told the Huffington Post the government was trying to “sideline opposition in Parliament by rigging the committee system so that they are guaranteed a majority they didn’t secure at the ballot box”.
The proposal, put forward by Commons Leader Andrea Leadsom, for public bill committees would mean that where there was an odd number of MPs on the committee, “the government shall have a majority”.
The committees scrutinise legislation in detail and are an important part of the passage of bills through Parliament. The number of seats allocated to each party usually reflects the proportion of seats it has overall in the Commons.
Ordinarily this would mean the government has a majority and can get its legislation through the committees – but the Conservatives lost their majority in the June general election.
Without a majority on the committees, it would lose control of an important part of the legislative process.
With a packed programme of Brexit legislation ahead, the government has already been criticised for attempting to give ministers, rather than parliament as a whole, the power to amend a raft of EU laws.
BBC political correspondent Iain Watson said the government will not want its legislation to be bogged down by the opposition as Brexit approaches and, with the support of the Democratic Unionist Party which has agreed to support the Conservative minority government, it was perfectly possible the proposal will go through next week.