Downing Street has been branded “absolutely deluded” for claiming the government has a Commons majority when it does not.
Theresa May is under-fire from opposition parties for plans to stack crucial Commons committees with Tory MPs - despite having failed to win a majority at the general election.
Jeremy Corbyn has accused the prime minister of trying to “rig” parliament with the plan to give almost unprecedented power to a minority government.
But No.10 said today it was “common sense”.
On Thursday HuffPost UK revealed May hopes to rip up a long-standing convention that the proportion of MPs from each party on the committees that vote on legislation reflect the general election result.
Having failed to win a majority in June, the Conservatives would be denied a majority on the committees.
However the government plans would change this.
Without a majority on the committees, ministers fear that all of their Commons business risks grinding to a halt or being gridlocked by Labour amendments.
The prime minister’s spokesman said because the government has a “majority on the floor of the House” it was therefore “perfectly legitimate” the government “should also have a majority in committees”.
However as Dr Ruth Fox, the director and head of research at the Hansard Society, told HuffPost UK, the government “does not have an outright majority”.
Instead it is propped up in power by the eight Democratic Unionist Party (DUP) MPs who agreed to side with the government on votes.
With the help of the DUP, May has a working majority of just 13.
It is unclear whether the Northern Ireland party has pledged to support proposed change to committees.
Corbyn attacked the plan as an “attempt to rig Parliament”. The Lib Dems said it was an “affront to democracy”.
Labour MPs expressed outrage at both the initial plan and also Downing Street’s defence.
Shadow health secretary Jonathan Ashworth said No.10′s argument showed “Theresa May is on a different planet”.
And former shadow cabinet minister Maria Eagle said it was “absolutely deluded”.
Dr Fox said while Downing Street’s claim the government had a majority in the Commons was wrong, it was “by some distance the largest party” and there were “precedents” for what it was attempting to do.
“In 1974 a minority Labour government had a majority on the Committee of Selection,” she said.
“When John Major’s government lost its majority in the early 1990s Committee arrangements continued to reflect the majority position it had secured at the start of the Parliament.
“In 1976 the Labour government lost its majority when John Stonehouse MP crossed the floor but the Committee of Selection continued to operate as if it had a majority.
“When the Chair of that Committee subsequently died political disagreement about the balance between the parties did break out. But that was eventually settled by a motion not that dissimilar to Tuesday’s motion.”
However Lib Dem chief whip Alistair Carmichael said that “with every day that passes this government gets further from the basic principles of democracy”.
“They want to pretend that the election never happened in order to try and ram through a destructive hard Brexit. It is an affront to democracy.
“We will fight tooth and nail to ensure parliamentary committees reflect the will of the electorate and do not simply rubber stamp government decisions.”
Shadow Leader of the House, Valerie Vaz told HuffPost UK: “This is an unprecedented power grab by a minority government that lost its moral authority as well as its majority at the General Election.
But a spokeswoman for Commons leader Andrea Leadsom, who is in charge of pushing through the change, told HuffPost UK: “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.”
With the support of the DUP, the plan to change how committees are constituted could succeed when put to a knife-edge vote late on Tuesday night.