Boris Johnson is under mounting pressure to give Parliament greater power to debate and vote on coronavirus restrictions, with more than 50 Tory MPs signalling they could revolt on the matter.
Conservative rebels seized upon an assessment by academics at University College London (UCL) which concluded that "Parliament has been consistently sidelined during the pandemic".
MPs will vote on Wednesday on whether to renew the Coronavirus Act, and dozens of Conservatives have signed up to an amendment tabled by Sir Graham Brady, chairman of the influential Tory backbench 1922 Committee, calling for ministers to consult Parliament before introducing new curbs on people's freedoms.
The size of the rebellion could see the Government facing defeat if the amendment is selected for a vote and opposition parties join forces with Sir Graham.
Tory former minister Steve Baker, one of more than 50 Conservatives signed up to the amendment, told the PA news agency he believed the Government will be forced to back down.
"I have always hoped we would find a way through to prior parliamentary approval," he said.
"I'm more optimistic now the UCL Constitution Unit has said we are right."
A blog post by the UCL's Professor Meg Russell and Lisa James said: "MPs have genuine cause for complaint."
They pointed to the new rules which came into force on Monday, but which only appeared in regulation form on Sunday.
"Only yesterday regulations on self-isolation were published, coming into effect just seven hours later, and imposing potential £10,000 fines; yet, despite media briefings eight days previously, these were not debated in Parliament," they said.
"Such cases raise clear political questions, but also legal ones: as the underlying legislation allows ministers to bypass Parliament only if a measure is so urgent that there is no time for debate."
They added that decisions to sideline Parliament were part of a "longer-running trend" under Mr Johnson.
"In his first six months as Prime Minister, Johnson cancelled or indefinitely postponed three Liaison Committee evidence sessions, unlawfully prorogued Parliament, and introduced a Withdrawal Agreement Act which – unlike its predecessor – gave Parliament no real oversight of this year's Brexit negotiations," they said.
"All this already suggested a reluctance to face parliamentary scrutiny."
Former chief whip Mark Harper said he would add his weight to Sir Graham's amendment unless ministers convinced him they were willing to change course when coronavirus is debated in the Commons on Monday afternoon.
He told the BBC's Westminster Hour: "If the Government is effectively prepared to commit to what the amendment says, great.
"But if not then I will support it as well. I think it's very important that when we're making what is the criminal law with quite important sanctions though, I think it's important that Parliament makes those decisions."