LONDON (Reuters) - British Prime Minister Keir Starmer said a landmark ruling that the legal definition of a woman under equality laws should be based on biological sex provided much-needed clarity and a clear position to underpin gender policies.

The Supreme Court ruled on April 16 that single-sex services for women, such as refuges, hospital wards and sports, could exclude trans women, clearing up legal ambiguity.

Starmer, in his first comments since the ruling, said he welcomed it. "I think for those that are now drawing up guidance, it's a much clearer position," he told broadcasters. "We can move on from there and I think that's been very helpful, and I would welcome that."

The judgment, which followed action by the "For Women Scotland" group, was welcomed by those who have argued that transgender policies have infringed on the rights of biological women.

Trans rights campaigners, however, said the ruling would have harmful implications on both a legal and practical level, and could lead to trans people being excluded from parts of society.

The Supreme Court stressed that the Equality Act afforded trans people - whether trans women or men - protection against discrimination or harassment.

Starmer has previously struggled to adopt a clear position on the definition of a woman amid the complex debate around gender and the rights of trans women and biological women.

He told the Sunday Times in 2023 that "for 99.9% of women, it is completely biological ... and of course they haven't got a penis".

Later that year his position had changed - he told BBC radio: "Firstly, a woman is an adult female, so let's clear that up."

On Tuesday, he said the court had "made it absolutely clear" that a woman was an adult female.

Public bodies, such as health services, will have to review their policies on single-sex spaces following the ruling.

Equalities Minister Bridget Phillipson told BBC radio the Equality and Human Rights Commission "will be setting out additional guidance and a statutory code of practice" to ensure everyone had the ability to access services that were safe and appropriate.

(Reporting by Paul Sandle; editing by Mark Heinrich)