A Labour MP was right to call Boris Johnson a liar in the Commons, party leader Sir Keir Starmer has said.

Sir Keir backed Dawn Butler, who was kicked out of the chamber last week for refusing to withdraw her claim that the prime minister has “lied to the House and the country over and over again”.

“I agree with what Dawn had to say,” he told LBC.

“I think the prime minister is the master of untruths and half-truths, and Dawn was simply giving some examples of that.

“I think there’s a lot of people that feel that, you know, it’s the person who’s not telling the truth rather than the person who’s calling it out that ought to be on the hotspot. So, I agree with Dawn on that.”

Brent Central MP Ms Butler was asked to withdraw her remarks several times by temporary deputy Commons Speaker Judith Cummins but refused to do so, resulting in her being asked to leave the chamber for the rest of the day.

Under parliamentary etiquette rules, it is not permitted for one MP to call another a liar.

Sir Keir added: “In fairness to the temporary speaker, Judith Cummings, who was there, she did the right thing, she followed the rules because parliament doesn’t allow you to call other parliamentarians liars in the chamber, so I don’t criticise the speaker … the deputy speaker for what she did, she was following the rules. But do I support Dawn in what she said? I absolutely do.”

Ms Butler, a former member of the shadow cabinet, tweeted in the wake of the incident: “I have been thrown out of Parliament for saying what we all know: Boris Johnson has lied to the House of Commons and the country over and over again.

“But I’ve got news for the Tories, I will never stop speaking truth to power!”

In a video posted on social media later on Thursday, she added: “I am just leaving parliament now because I have been thrown out for calling Boris Johnson a liar.

“But he is a liar. He’s lied to the House and the country over and over again and I’ve had enough and I had to call it out – so, I’m leaving parliament.”