In a final humiliation on Monday MPs backed a damning report which found Mr Johnson had lied to Parliament over and over again - stripping him of his Westminster pass.
He faced accusations he was "too weak" to stand up to his predecessor and his "sycophants" within their fractious party.
Since them No 10 has refused to be drawn on the prime minister’s personal view or how he would have voted.
After he was asked about Mr Johnson at PMQs, the Prime Minister's press secretary said: "He respects the view of the House that was taken on Monday and it's right that members (of Parliament), whoever they are and whatever position they have held, are held to account for their actions."
She would not set out whether or not he agreed with the committee's report, however, saying he "respects" the view of the House.
Mr Johnson dodged the recommended 90-day suspension by quitting his Uxbridge and South Ruislip seat.
In the end 354 MPs backed the Partygate report, while just seven voted against it - a majority of 347.
Tory MPs who supported Mr Johnson included Sir Bill Cash, Nick Fletcher, Adam Holloway, Karl McCartney, Joy Morrissey and Heather Wheeler.
Mr Sunak was accused of "running scared" of the showdown in parliament on Mr Johnson, with No 10 claiming he had been too busy hosting the Swedish prime minister to attend.
The PM said at the weekend that he did not want to "influence anyone" when pressed on how he would vote on the report, which found Mr Johnson lied to parliament and undermined the committee's work with personal attacks.
One former prime minister, Theresa May, did turn up to condemn Mr Johnson - arguing that her successor had been "found wanting" and urging all Tory MPs to back the report to help "restore faith in our parliamentary democracy."
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