Boris Johnson has been told by a senior Tory backbencher that his leadership will be "on the table" if the Government does not back off on Covid restrictions.
Steve Baker of the lockdown-sceptic Covid Recovery Group has written to members urging them to put pressure on the Tory chief whip over the issue.
Mr Baker, who played a prominent part in Theresa May's downfall, warned that unless the issue was dealt with now it would become a matter of leadership.
He stated in the letter to colleagues: "I am sorry to have to say this again and as bluntly as this: it is imperative you equip the Chief Whip today with your opinion that debate will become about the PM's leadership if the Government does not set out a clear plan for when our full freedoms will be restored, with a guarantee that this strategy will not be used again next winter."
Railing against the prospect of increased coronavirus restrictions, Mr Baker said: "If we continue forward with a strategy that hammers freedom, hammers the private sector, hammers small business owners and hammers the poor, inevitably the Prime Minister's leadership will be on the table: we strongly do not want that after all we have been through as a country."
As it appeared ministers were prepared to approve new coronavirus measures, he said: "I am sorry to be blunt but if we do not act now, events will become inevitable. For the good of the country please contact the Chief Whip.
"We must take stock today and act now to avoid severe problems a little later.
"Certain Government scientists have said that 'the current lockdown could last until late spring'. There is no reason to think there will be any real resistance in Cabinet to the argument for greater and longer and more draconian restrictions on the public.
"This could be a disaster. Nothing seems more certain to break the public than giving hope before taking it away, and doing it repeatedly.
"Government has adopted a strategy devoid of any commitment to liberty without any clarification about when our most basic freedoms will be restored and with no guarantee that they will never be taken away again.
"People are telling me they are losing faith in our Conservative Party leadership because they are not standing up for our values as a party."