A former Norfolk Conservative MP has said prime minister Boris Johnson "has no shame" and is "amoral".
And he said the days ahead could further damage his former leader's chances of staying in power.
Mr Johnson said he took “full responsibility” after the report by senior official Sue Gray revealed details of a series of parties in No 10 during the coronavirus lockdown.
The prime minister has resisted faced fresh calls to resign, but one of his former Tory colleagues said the scandal could yet bring about his exit.
Keith Simpson, MP for Broadland from 2010 to 2019 and MP for Mid Norfolk from 1997 to 2010, said: "I don't think he should have led the party into the last general election, let alone the next one.
"The problem is, I think he is an amoral individual. He ducks and dives and David Cameron was right to describe him as a greased piglet. He has no shame.
"In my experience of working in organisations, when things go right or things go badly, the way the man or woman at the top behaves determines the atmosphere of the organisation."
Mr Simpson said: "He is never going to resign. The only way he will be removed is when a significant number of Conservative MPs decide he has no longer got it in him to return them to their seats and win the next election.
"This has undoubtedly damaged him, but we will find out, in the next few days, when MPs go back to their constituencies, just how much.
"Their own Conservative associations may well be very angry and I think the majority will be fed up with having to defend him in public."
Mr Simpson said defeat for the Conservatives in the Wakefield and Tiverton by-elections would pile on further pressure - and there remains the matter of the Commons committee investigating whether he misled parliament.
But Mr Simpson added: "What could really be the killer for him is inflation and the cost of living crisis.
"The fact [chancellor] Rishi Sunak may be making a statement on Thursday might be convenient, but they really have got no idea how to deal with it and they are in a big hole on this.
"They will run out of road with the public. And remember, it's not like they're only a year or two into this - they have been in power for 12 years."
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