A furious row has erupted between two Labour MPs after Samantha Niblett, the politician who called for a “summer of sex,” hit out at new transgender guidance.

Single-sex toilets, changing rooms and hospital wards must now be used based on a person’s sex at birth and not the gender they identify as, under a new statutory code which came into force on Wednesday.

Ms Niblett, the Labour MP for South Derbyshire who is pushing for lifelong sex education, attacked the code and said it would “cause more division and hatred towards trans people.”

But her intervention prompted fellow Labour MP Tonia Antoniazzi, one of the most high-profile backers of single-sex protections, to accuse her of having “lied about me in the media”.

In a video, posted from a sunlounger while on holiday, Ms Niblett said: “This new guidance protects nobody. All it does is cause more division and hatred towards trans people that just want to have their life, minding their own business, and protects no cis woman who is gender critical — let’s call it what it is, hates trans people, like, because if you didn’t, why would you fear trans people?”

She added that she was “so unbelievably ashamed” of politicians’ responses and said: “I promise you I will continue to use my platform as an MP to fight for the rights of trans people.”

“Don’t kid yourself, ladies. They’re coming for you after they come for the rest of the LGBT community. They’re coming for you. They’re coming for us. Stop pretending this is about protecting women’s rights. It’s nothing of the sort.”

In response, Ms Antoniazzi, the Labour MP for Gower, posted on X, formerly Twitter: “You’ve lied about me in the media. I have receipts. Have a good break, MPs deserve it. Today, we have clarification, not more confusion. Women and girls need protection from men, stop using trans people as an argument for your pro-sex work, pro-porn agenda.”

It is thought her criticism refers to a statement Ms Niblett made about her in a recent interview.

The changes are being implemented more than a year after a landmark Supreme Court ruling on biological sex, concluded that transgender women are not legally women under the Equality Act.

The new code has been produced by the Equality and Human Rights Commission’s (EHRC).

Nadia Whittome, the MP for Nottingham East, said it marked “a dark day for trans people”, while other MPs have welcomed the guidance which they argue does not change anything but rather clarifies the existing law.

Ms Niblett made headlines when she suggested that fellow parliamentarians bring sex toys to the Palace of Westminster and called for “a summer of sex”.

She has since joked about being branded “the sex MP“ but warned of the important lifelong sex education that is needed to tackle abuse and problems with sex and relationships.

She recently became chair of the All-Party Parliamentary Group on Sex and Reproductive Health, and has won the backing of actress Dame Emma Thompson and specialists for her campaign, Yes Sex Please, We’re British! campaign.