The former charity representative took to social media to announce the step down, writing: “I would like to confirm that I have recently stepped down from my role as Parliamentary Advisor to Endometriosis South Coast.

“It was not a decision taken lightly, but one I believe is in the best interests of myself, the charity, and the vital work it does in supporting those living with endometriosis.

“I wish the organisation and everyone it serves well.”

This comes after the former charity representative had dismissed the criticism of the appointment as “transphobic”.

Richards, who founded and was CEO of Translucent, an advocacy group focusing on trans and human rights, will be now working “closely” with Women’s Action Network Portsmouth (WANP).

Among the criticism of the appointment, Suella Braverman, Reform’s spokeswoman for education skills and equalities, called for the charity to re-think Richard’s role last month.

She wrote: “It is remarkable that a charity established to advocate for women’s health would appoint a man, without female anatomy or experience of this disease, to speak for those whose suffering is defined by their sex.

“This regressive decision erases women from their own health issues, replaces lived female experience with male self-identification and silences the very people your organisation claims to represent.”

Ms Braverman also posted on X: “With respect to him, this person is a man. I have no problem with what he wears or what he does in private. But he is a man. And it is not transphobic to say so.

“It is insulting and inappropriate to the 1.5 million women who suffer with endometriosis for him to have been appointed to speak for them.”

The charity has also confirmed the move, writing in a statement: “Endometriosis South Coast can confirm that Steph Richards has stepped down from her voluntary role as Parliamentary Advisor to the charity.

“We wish her well and thank her for her contribution to our work.”

Endometriosis “is where cells similar to those in the lining of the womb (uterus) grow in other parts of the body”, according to the NHS website.

It is a chronic condition, affecting one in 10 women, commonly causing severe pelvic pain, heavy periods and infertility by causing inflammation and scarring.

Often it takes women a long time to receive a diagnosis – Amanda Craig, award-winning novelist and vocal critic of the appointment, waited seven years before being diagnosed with endometriosis after doctors dismissed her as “a neurotic, middle-aged, middle-class woman”.

She said, speaking to the Times: “It’s fundamentally discordant and wrong.

“Even if it comes from a good place and wants to help women. This is something that’s so specific to the female experience.

“It absolutely needs to be represented by someone with lived experience of this horrible disease.”

Rosie Duffield, the independent MP for Canterbury, previously described Richards’ selection as “inappropriate”.

The former Labour MP said she felt “uncomfortable” when the charity representative invited her to a parliamentary event.

She said: “I am really uncomfortable that, of all of the tens of thousands of women affected, someone who is biologically male is coming to speak about this in parliament.”

Endometriosis South Coast previously said its new parliamentary envoy is a volunteer position and does not occupy a senior role or speak directly on behalf of those affected by the disease.

A spokesman rejected the premise only women experience endometriosis, calling such a claim “scientifically inaccurate”.

They said: “It affects people of all genders, including trans men, non-binary, and intersex individuals.”