Jacob Rees-Mogg has insisted that Boris Johnson would “comfortably” win a by-election in his Uxbridge and South Ruislip seat.
The former business secretary said Johnson would survive a vote in his constituency because he is “winning in the court of public opinion”.
However, Tory polling guru Lord Robert Hayward disputed this, saying that on the basis of current polls “we would lose the constituency”.
Rees-Mogg made his comments after the former prime minister was interrogated by seven MPs over whether he misled parliament about Partygate.
If the privileges committee decides Johnson did mislead MPs - and the Commons backs suspending him for 10 days or more - he could face a by-election.
Rees-Mogg told Channel 4 News: “I think that if Boris Johnson went to a by-election he would win it comfortably.
“Because I think he’s winning in the court of public opinion, who see this as a kangaroo court.”
However, Hayward said a by-election in Johnson’s seat could “cause serious problems” for the Conservative Party.
In an interview on Sky News, the Tory peer said: “The party doesn’t want a by-election.
“My guess is that if there were a by-election - certainly on current polls - we would lose the constituency and therefore it’s something that is there but we can’t prejudge what the committee will decide.”
Hayward also said he believed Johnson’s support was “diminishing” as well as his impact on the party the longer that Rishi Sunak is prime minister.
Johnson swore “hand on heart” that he did not lie to the House of Commons, at a high stakes hearing on Wednesday.
He swore on the King James Bible to tell the truth before issuing an apology and adding “hand on heart, I did not lie to the House”.
The backbencher went on: “When those statements were made, they were made in good faith and on the basis on what I honestly knew and believed at the time.”
The committee is expected to report after Easter.