Rishi Sunak has refused to apologise for making a transgender joke in the Commons while the mother of murdered teenager Brianna Ghey visited Parliament, as Number 10 called the jibe at Labour “totally legitimate”.

The Prime Minister accused Sir Keir Starmer of having difficulty in “defining a woman” during an attack on Labour party U-turns, while Brianna’s mother watched from the Commons gallery.

The remarks prompted an immediate backlash, but Downing Street doubled down on the comments and insisted the joke was not transphobic.

Mr Sunak said: “We are bringing the waiting lists down for the longest waiters and making progress, but it is a bit rich to hear about promises from someone who has broken every single promise he was elected on.

“I think I have counted almost 30 in the last year. Pensions, planning, peerages, public sector pay, tuition fees, childcare, second referendums, defining a woman – although in fairness, that was only 99% of a U-turn.”

The Labour leader, who met Brianna’s mother Esther Ghey on Wednesday, condemned the Prime Minister’s remark, with a chorus of opposition backbenchers calling out: “Shame.”

Number 10 declined repeatedly to apologise for Mr Sunak’s language and said it was part of a “legitimate” criticism of Labour.

Mr Sunak’s press secretary said: “If you look back on what the Prime Minister was saying, there was a long list of u-turns that the leader of the opposition had been making.

“I don’t think those U-turns are a joke, it is quite serious changes in public policy. I think it is totally legitimate for the Prime Minister to point those out.”

“It is clearly part of what happens in the chamber, at prime minister’s questions, to point out the u-turns an opposition leader has made,” she added.

The Labour leader immediately rebuked Mr Sunak for the joke.

“Of all the weeks to say that, when Brianna’s mother is in this chamber. Shame.

“Parading as a man of integrity when he’s got absolutely no responsibility.”

Sir Keir added: “I think the role of the Prime Minister is to ensure that every single citizen in this country feels safe and respected, it’s a shame that the Prime Minister doesn’t share that.”

The Prime Minister also faced calls to apologise from Labour MP Liz Twist during the session but did not directly respond to her call.

But concluding Prime Minister’s Questions, he said: “If I could just say also to Brianna Ghey’s mother who is here, as I said earlier this week, what happened was an unspeakable and shocking tragedy.

“As I said earlier this week, in the face of that, for her mother to demonstrate the compassion and empathy that she did last weekend, I thought demonstrated the very best of humanity in the face of seeing the very worst of humanity.

“She deserves all our admiration and praise for that.”

Cabinet ministers defended their party leader in the wake of the exchange, with Business Secretary Kemi Badenoch accusing Labour of trying to “weaponise” the issue.

Ms Badenoch, who is also Equalities Minister, said on X: “Every murder is a tragedy. None should be trivialised by political point-scoring. As a mother, I can imagine the trauma that Esther Ghey has endured.

“It was shameful of Starmer to link his own inability to be clear on the matter of sex and gender directly to her grief.”

Chancellor Jeremy Hunt also told ITV News: “It was the most appalling tragedy and I think everyone has been incredibly struck by the courage and resolve of Brianna’s mother, Esther, throughout the whole of this terrible, terrible story.

“And we should also be clear, the Prime Minister was not talking about that; he was talking about the fact that Keir Starmer has changed his position on that, as on many other issues.”

But Mr Sunak did face some criticism even from within his party ranks.

Former Tory business minister Jackie Doyle-Price said it was “careless” and “very ill-judged” for him to use the joke “in that context”, but also accused critics of having “weaponised” it.

“I find this pre-rehearsed line on this issue really trivialises something that’s very important so I’ve become more uncomfortable with that,” she told Times Radio.

“To say it in that context was just, frankly, very ill-judged, but I was equally uncomfortable with the way that it was weaponised. And I just think what an ugly situation all around, because, you know, there is a dead child here who’s been murdered in the most appalling circumstances. And for that to be the exchanges in the in the chamber of the House of Commons, it’s just not my proudest moment to be a member of Parliament I must say.”

Former junior minister Dehenna Davison, in a post on X, formerly Twitter, said it was “disappointing to hear jokes being made at the trans community’s expense” and warned that “our words in the House resonate right across our society”.

The Bishop Auckland MP, who was not in the chamber on Wednesday, said: “As politicians, it’s our job to take the heat out of such debates and focus on finding sensible ways forward, whilst ensuring those involved are treated with respect.

“Given some of the terrible incidences of transphobia we have seen lately, this need for respect feels more crucial than ever.”

This is not the first time the Prime Minister has attacked Labour over the issue of gender identity policies, which have been a frequent subject of debate in Westminster in recent years.

LGBT campaigners have condemned some of the language used by politicians to discuss transgender people, with the issue often drawn into the so-called “culture war” by right-wingers.

In his Tory conference speech last year, Mr Sunak told Conservative delegates in Manchester “We shouldn’t get bullied into believing that people can be any sex they want to be.

“They can’t – a man is a man and a woman is a woman.”

A Labour spokeswoman called on Mr Sunak to apologise.

“We don’t think the country wants or deserves a Prime Minister that is happy to use minorities as a punchbag,” she said.

LGBT+ charity Stonewall called Mr Sunak’s words “cheap, callous and crass”.

A spokesperson said: “The disrespect and dehumanisation of trans people that we see played out daily in the media and in our political discourse has real-life consequences and it has to stop.

“We call on the Prime Minister to apologise unreservedly for his comments, and for him to reflect on how careless words from those in power can and do result in harm.”