Some of these bodies retain outdated policies permitting biological males who identify as transgender to access female-only facilities, including changing rooms and toilets.

Women’s rights campaigners have condemned the findings as “inexcusable”, accusing institutions of demonstrating “complete disregard for the law” that has caused “untold harm to women and girls”.

Shadow Equalities Minister Claire Coutinho said: “The Supreme Court ruling was meant to put an end to this madness. Cowardice, obfuscation, and a complete lack of grip. That is all the Labour Party has to offer women’s rights.”

The Supreme Court established in April last year that sex under equality legislation refers to biology rather than self-identification or possession of a gender recognition certificate.

The scale of non-compliance was particularly pronounced across the 190 NHS trusts with inpatient facilities in England, where 97 per cent maintain policies that allow trans-identifying biological males access to women-only spaces.

Over half of England’s 317 councils have failed to bring their practices into line with the court’s decision, while more than 20 of the 43 police forces across England and Wales confirmed they had not yet revised their policies.

Gwent Police in Wales openly acknowledged it was disregarding the ruling, stating: “Our policy remains the same. Staff and officers use facilities in accordance with their lived gender.”

Meanwhile, internal civil service guidance is currently “under review”, and no Whitehall department was able to confirm it had fully implemented the Supreme Court’s decision.

Conservative leader Kemi Badenoch accused Labour of failing to provide leadership on the issue.

She said: “A year after the Supreme Court’s clear ruling, too many public bodies are acting as if the law is optional because Labour has failed to lead. The law is not optional – it must be enforced.”

Helen Joyce, of the advocacy charity Sex Matters, said the failure to adopt biology-based policies had caused “untold harm to women and girls.”

Much of the blame centres on delayed guidance from the Equality and Human Rights Commission, which ministers have held since September without publishing.

Equalities Minister Bridget Phillipson indicated this week she intends to release the guidance next month.

However, Cathy Larkman from the Women’s Rights Network described the situation as “inexcusable”, adding: “A year after the judgment, the excuses have run out.”

Several NHS trusts continue operating policies based on self-identification, such as Stockport NHS Foundation Trust’s guidance stating non-binary individuals should be allocated to wards “according to their choice”.

Tameside and Glossop Integrated Care NHS Foundation Trust’s policy directs that trans people be accommodated “according to their adopted identity.”

Both trusts confirmed their policies were under review.

Former EHRC chair Baroness Falkner disclosed at a parliamentary event marking the ruling’s anniversary that she had no discussions with the minister about the guidance between submitting it in early September and leaving her post at the end of November.

“You knew something was up, the fact that the minister wouldn’t discuss it with you,” she said.

“In my previous experience with two different secretaries of state and different ministers of state, including ones who completely disagreed with the direction of travel, there’d always been conversations. This was a remarkable turn of events.”

Susan Smith, founder of For Women Scotland, the organisation that brought the case to the Supreme Court, said: “It’s shocking that public bodies are using the discredited excuse that they need to wait for guidance to follow the law. They don’t. The ruling is crystal clear.”

NHS England acknowledged it was “working through the implications of the ruling”, and recognised the need for revised same-sex accommodation guidance “as soon as possible.”

A Government spokesman said: “We have always supported the protection of single-sex spaces based on biological sex.”