Former PM Sir John Major lashed out at Tory ex-ministers for only ousting Boris Johnson when it was "self-damaging" to stay quiet.
The ex-Tory leader told a committee of MPs the blame for "lapses" in standards lay "principally but not only with the Prime Minister".
But he lashed out at Mr Johnson's former ministers and supporters, saying: "Many in the cabinet are culpable too and so are many outside the cabinet who cheered him on.
"They were silent when they should have spoken out and then spoke out only when their silence became self-damaging."
Sir John appeared before the Public Administration and Constitutional Affairs Committee (PACAC), who have been investigating standards in government since the Greensill lobbying scandal, which involved his Tory successor David Cameron.
Last week, Sir John made an intervention in the Tory leadership contest, urging the party's 1922 committee to quickly remove Mr Johnson from office, and saying it would be "unwise" to allow him to stay in Number 10 until a successor is selected.
And he questioned whether Cabinet Secretary Simon Case could truly have been "shocked" when he read Sue Gray's partygate report, as he said at a previous hearing.
Asked whether this was credible, Sir John said: "I think it pushes the elastic a long way."
He added: "It's quite difficult to accept that there were as many things happening in lockdown as the Sue Gray report set out with people being utterly unaware that that was the case."
Sir John said such unawareness would have constituted "a remarkable disinterest in one's working habitat".
