The DUP will back the Conservatives in a vote later on changing the make-up of committees which scrutinise government legislation, the BBC has learned.
The government wants to ensure there is a Tory majority on the committees – even though the party does not have a majority on its own in Parliament.
Labour’s Jeremy Corbyn has accused ministers of an “unprecedented attempt to rig Parliament”.
But a senior DUP source described the party’s support as “uncontroversial”.
The row was sparked by a motion which will come before MPs for a crunch vote on Tuesday.
Tabled by Commons leader Andrea Leadsom, it states that Commons rules will be changed so that “where a committee has an odd number of members, the government shall have a majority”.
And “where a committee has an even number of members, the number of government and opposition members shall be equal; but this instruction shall not apply to the nomination of any public bill committee”.
If MPs back the rule change, the public bill committees, which scrutinise legislation line by line, would no longer mirror the make-up of the Commons, but have an in-built Conservative majority instead.
This would allow Mrs May to force through legislation without fear of opposition amendments if Tory committee members remain loyal.
Theresa May has rejected claims the move is an “unprecedented power grab”, insisting the government has a majority in the Commons, even though it needs the backing of 10 DUP MPs on key issues.
“What we are doing is ensuring the government’s working majority is available across the business in Parliament,” she said.
Avoiding trench warfare?
But Mr Corbyn said: “The Conservatives didn’t win the election. They are the largest party, they don’t have an overall majority in Parliament.
“They’ve done a deal with the DUP which involved £1bn of money being spent in Northern Ireland and not in the rest of the country and now they think they’ve got the right to give themselves a majority in the committee in Parliament.
“It’s not so – we’re a Parliament, a hung Parliament and the committees should reflect that, and there should be no overall government majority on the committees.
“They should get what’s due to them, which would be the largest number of places, but not a majority.”
A senior DUP source told the BBC the party’s support for the Tories was “uncontroversial” because “the alternative would be spontaneous trench warfare on the most mundane of issues, and to whose benefit? Jeremy Corbyn’s benefit. And we’re not in the business of doing that”.
A Commons media spokeswoman said the minimum number of members on a Public Bill committee is 16, while the maximum is 50.
The Commons Committee of Selection, which nominates members to general and select committees, has discretion over whether to appoint an even or odd number of members, she said.
“This will of course be dependent on the numbers received from the parties,” the spokeswoman added.
Odds or evens?
In the 2016-17 session, there were 31 public bill committees with numbers as follows:
- 16 members: 21 committees
- 18 members: seven committees
- 19 members: one committee (Digital Economy Bill)
- 20 members: one committee (Higher Education and Research Bill)
- 25 members: one committee (clauses of Finance Bill)
Lib Dem leader Sir Vince Cable claimed there was some unease among Tories about the motion to change the parliamentary rules.
“We know there is some disquiet and our people in Parliament are obviously talking to other people about it,” he said.
“It is very worrying – you have a minority government seeking to impose its will in this really quite authoritarian way.
“One of the most revealing episodes about this legislation at the moment is people who spent their whole lives in Parliament talking about parliamentary sovereignty are now selling it down the river.”