Cancer screenings have been missed and criminal convictions overlooked because of how data is collected about people's biological sex and gender identity, an independent review found.
The review, led by Prof Alice Sullivan, outlined the risks of conflating biological sex and gender when it comes to clinical care, sex-specific cancer screening and safeguarding.
Prof Sullivan, a professor of sociology at University College London, urged public bodies to collect data on both sex and gender identity by default "across the board" to ensure it is accurate.
The Department of Health said the findings would be considered with "the gravity they deserve, as it reforms gender identity services across the board".