In a letter to Holyrood’s culture committee, eight senior academics from Glasgow, Heriot Watt and Edinburgh universities said proposed changes to the census sex question may mean statisticians using census data are less able to monitor "sex-based discrimination and disadvantage", the Scotsman reported.

The group said in the letter they supported the decision to retain a binary question on sex, but stressed it must ask the public "about legally-recognised sex, rather than self-identified".

They added: "The census has a unique importance in the statistical system. It is the only source providing full coverage of the population on such a wide range of aspects of social life and therefore it is uniquely well-placed to provide information on smaller population groups. At the same time, it is the foundation on which many other statistics about our society are built."

The researchers welcomed the proposed addition of a voluntary question on transgender identity, which was agreed earlier this year.

While the 2021 census will keep the binary male/female question to gather data on sex, it is not yet clear what guidance will be given on how to answer the mandatory question. The National Records of Scotland has proposed respondents should answer based on how they self-identify.