Tory MPs have urged Harriet Harman to step back from an inquiry into whether Boris Johnson misled parliament, after unearthing historic comments by her on the matter.
The veteran Labour MP was accused of prejudging the outcome of the investigation after it emerged in April she had posted that Mr Johnson appeared to have "misled the House of Commons".
Ms Harman was put onto parliamentary privileges committee this week to replace Chris Bryant, who was recused after having called Mr Johnson a "proven liar" who "repeatedly lied to parliament".
Sir Robert Buckland, the former justice secretary, told the Daily Telegraph newspaper that Harman should “reflect” on her position as the committee's likely chair.
“As a lawyer, Harriet Harman is someone who values due process above everything else and I am sure she would want to reflect very carefully about any potential impact of tweets she has issued that in any way suggest that she is biased,” he said.
And on Thursday morning Cabinet office minister Michael Ellis told MPs Ms Harman should "consider" her position.
"It is an age old principle of natural justice that no person should be a judge in their own cause,” he said.
But Labour frontbencher Nick Thomas Symonds on Thursday morning defended his colleague.
"I think Harriet Harman is a highly respected, highly experienced parliamentarian. Which MP hasn't expressed views of different kinds about the Prime Minister?" he told Sky News
"The committee will continue its investigation. Harriet Harman is an extremely experienced, very well-respected, on all sides of the house [parliamentarian]."
Ms Harman had tweeted on 12 April: “If you get Covid regulations FPN you can either admit guilt, or go to court to challenge it. If the prime minister and chancellor admit guilt, accepting that police right that they breached regs, then they are also admitting that they misled the House of Commons. Or are they going to challenge?”
She also shared a blog posted by Alastair Campbell, the former Labour press secretary, in which he said the prime minister and others “broke their own emergency laws”, and “lied repeatedly”.
The prime minister repeatedly claimed in parliament that he had broken no rules and that he was upset at having discovered what had been taking place on No10 – deploying a sliding scale of excuses that retreated each time new evidence emerged. However, it later emerged that he had broken the rules personally, and that he was present at a number of the gatherings.