The cross-party group of MPs investigating whether Boris Johnson knowingly misled the Commons over partygate should be allowed to work without interference, Penny Mordaunt has said.

The Commons Leader warned MPs, peers and others against trying to prevent the investigation into the ex-prime minister from taking place.

Mr Johnson has agreed to face televised questioning by the Privileges Committee next Wednesday on whether he lied to MPs over partygate.

Asked about reported attempts to influence or intimidate the committee, Ms Mordaunt emphasised that MPs on the Privileges Committee “are doing this House a service”.

She added: “They need to be permitted to get on with their work without fear or favour and I would also remind members in this House that this House asked them to do this work.

“We referred this matter to the committee for them to consider and we asked them to do this work and to do it well, and they should be left to get on with this.

“That is the will of this House and I think a very dim view will be taken of either any member who tries to prevent them from carrying out this serious work or anyone from outside this House that interferes.”

Hinting at potential for interference by members of the House of Lords, the Commons Leader added: “On a personal level, an even dimmer view will be taken of anyone from the other place (the Lords) who attempts to do similar.”

Conservative MP Simon Hoare (North Dorset) had earlier raised concerns about interference with the committee’s work.

The chairman of the Northern Ireland Affairs Committee told MPs: “As chairman of a committee of this House, I know, and I hope that she does, the important, independent and cross-party work that all committees of this House do on behalf of the House, including the Privileges Committee.

“She will know there has been speculation about its current investigation which was approved, she will remember, without amendment or division in this House.

“Does she agree that members of the committee are doing the House a service, that they should be free and unfettered to get on with their work, and free of interference or intimidation?”

Mr Johnson and his allies have raised concerns over partygate investigator Sue Gray’s pending move to Labour leader Sir Keir Starmer’s office from the civil service.

However, the committee, chaired by Labour grandee Harriet Harman but with a Conservative majority of four of its seven MPs, denied its inquiry is based on the Gray report.

Instead, the inquiry has taken evidence from witnesses’ WhatsApp messages, emails and pictures from a Downing Street photographer.

The Prime Minister has said he will not try to exert influence over Tory MPs on the committee not to impose a large punishment.

“That wouldn’t be right,” Rishi Sunak told broadcasters in San Diego last week.

“This is a matter for Parliament, for the House. It’s not right for the Government to get involved.”