Transgender women should not be legally defined as women, the Supreme Court has ruled.

Handing down the court’s judgment on whether sex-based protections should only apply to people who were born female, Lord Hodge said the terms “woman” and “sex” in the 2010 Equality Act referred to biological sex, not acquired gender.

“The unanimous decision of this court is that the definition of the terms woman and sex in the Equality Act 2010 refer to a biological woman and biological sex,” he told the court.

“But we counsel against reading this judgment as a triumph of one or more groups in our society at the expense of another. It is not.

“As I will explain later in this handout speech, the Equality Act 2010 gives transgender people protection not only against discrimination through the protected characteristic of gender reassignment, but also against direct discrimination, indirect discrimination and harassment in their acquired gender.”

The case before the Supreme Court centres on whether transgender people with a gender recognition certificate (GRC) are women under the Equality Act 2010, one of its justices has said.

Lord Hodge told the court: “The central question on this appeal is the meaning of the terms woman and sex in the Equality Act 2010.

“Do those terms refer to biological women or biological sex? Or is a woman to be interpreted as extending to a trans woman with a gender recognition certificate?”

Sex is binary, the Supreme Court has ruled.

“The definition of sex in the Equality Act 2010 makes clear that the concept of sex is binary, a person is either a woman or a man,” the judgement reads.

“Persons who share that protected characteristic for the purposes of the group-based rights and protections are persons of the same sex and provisions that refer to protection for women necessarily exclude men.

“Although the word ‘biological’ does not appear in this definition, the ordinary meaning of those plain and unambiguous words corresponds with the biological characteristics that make an individual a man or a woman.

“These are assumed to be self-explanatory and to require no further explanation. Men and women are on the face of the definition only differentiated as a grouping by the biology they share with their group.”

It's the "unanimous decision" of this court that the terms "woman" and "sex" refer to a biological woman and biological sex in the Equality Act 2010, Lord Hodge says in the Supreme Court