The House of Commons was emotional as a Conservative MP made a moving tribute to Harriet Harman following attacks from Tories over Boris Johnson and partygate.

Conservatives allied to Johnson have suggested veteran Labour MP Harman, who chaired the privileges committee which found the former MP guilty of lying to parliament repeatedly, was biased because of tweets she posted about partygate before taking up the role.

On Monday, MPs approved the committee’s report that judged the former prime minister’s outriders had launched a “co-ordinated” attack on its work.

During a debate ahead of the report being nodded through without the need for a vote, Conservative MP Laura Farris made an intervention damning her Tory colleagues.

Harman has long been aware of the potential issue – and asked the government for the green light to continue as chair of the committee investigating Johnson.

Harman said she wanted to avoid the “perception” that she was biased against the former PM – and was “assured that I should continue the work” by the prime minister at the time, which was still Johnson.

During Monday’s debate, Jacob Rees-Mogg, a Johnson loyalist who was criticised for his role in the attacks on the committee, maintained it was “legitimate to question” Harman’s position.

But Farris took a different view, defending Harman and paying tribute to her career – with her parliamentary colleague close to tears as a result.

Farris said: “The member for Camberwell and Peckham (Harman’s constituency) had already announced her intention to retire from parliament at the next election.

“A parliamentary career that has spanned five decades and has been defined by her commitment to the advancement of women’s rights.

“Fourteen weeks before she took up that appointment (as committee chair) her husband of 40 years, Jack, had died.

“Against this background, I invite members of the House to consider what is more likely – that she agreed to chair the committee as a final act of service to this House, or that she did so because she was interested in pursuing a personal vendetta against Boris Johnson.”

Farris continued: “It is completely unacceptable to allege or insinuate that members of the privileges committee are corrupt or that the inquiry was somehow rigged.”

Harman’s husband, Labour MP Jack Dromey, died suddenly in his flat in Birmingham in January last year.

The initial report by the privileges committee, which has a Conservative majority, suggested Johnson should face a 90-day Commons suspension if he had not already quit parliament ahead of its release.