Maya Forstater, a tax expert previously contracted by the Center for Global Development. (Twitter)

A tax-avoidance researcher who claims she lost her job at a think tank for saying that trans women aren’t women has told an employment tribunal “there is one sex or the other”.

At the employment tribunal hearing, Maya Forstater, 46, said she agreed that the trans community was vulnerable.

She added: “I don’t think it’s possible for someone to change their sex … [although] it’s possible to change it on a birth certificate.”

Forstater was a visiting fellow at the Centre for Global Development when her contract was not renewed in March this year, after a dispute over tweets she sent opposing government proposals to reform the Gender Recognition Act and make it easier for trans people to change their legal gender.

In September 2018, Forstater wrote on Twitter: “I think that male people are not women. I don’t think being a woman/female is a matter of identity or womanly feelings. It is biology.”

Forstater also tweeted that the “truth” was “that men cannot change into women” and said that transgender women are not women.

This was part of a series of over 100 tweets from Forstater protesting proposed reforms to the Gender Recognition Act that could make it easier for transgender people to change their legal gender.

Following her tweets, an email from a manager at the think tank said: “You stated that a man’s internal feeling that he is a woman has no basis in material reality. A lot of people would find that offensive.”

Her discrimination case against CGD, which started being heard yesterday (November 15) in central London, is being funded with money she raised through the CrowdJustice website.

Forstater previously said that she hoped the case might establish that “gender-critical views” are a protected belief under the 2010 Equality Act.

In her statement provided to the court, Forstater said: “When I had thought about transgender people, I had understood them to be their biological sex and I would treat people in the way they would like to be treated.

“But I did not think people could literally change sex.

“I did not think about it much because I did not think anybody thought that people could literally change sex.

“From the earliest I can remember, I have understood that there is one sex or the other.”

CGD has said it supports diversity and equality and disputes Forstater’s claims. It argues that her opinions upset other employees and were not consistent with its values.

The hearing continues.