MSPs voted unanimously to pass the census bill, which includes the provision for the questions to be asked on a voluntary basis in the 2021 census in Scotland.

The bill will amend the 1920 Census Act to enable National Records of Scotland (NRS), which is responsible for the census, to ask the questions. 

While passing the bill removes the penalty for not responding to the new questions, parliament still has to agree on the wording of the questions. The NRS will put final proposed questions before Holyrood for agreement before the census takes place.

Since the census bill was introduced in October 2018, there have been concerns raised over whether the mandatory question about sex should include a non-binary response option as well as the binary male/female response options – a proposal that had been raised by the NRS.

Holyrood’s culture, tourism, Europe and external affairs committee has recommended that the sex question should remain binary.

There is still debate over what guidance should accompany the questions, including whether individuals should complete the sex question on the basis of their biological sex or their ‘lived sex’.

Professor Susan McVie, chair of quantitative criminology at the University of Edinburgh, who sits on the government’s board for official statistics, wrote in a letter to MSPs: "I strongly urge the committee to support the retention of a binary sex question based on biological/legal sex. Sex refers to clear biological and physical characteristics and is a protected characteristic under the Equality Act 2010.

"This is a clear and separate issue from gender-identity, which is a much more complex social construct that is underpinned by a range of physical, social, psychological and cultural factors."

Voluntary questions on gender identity and sexuality will also be included in the 2021 census in England and Wales, although the Office of National Statistics has ruled out a non-binary response option.

Fiona Hyslop, cabinet secretary for culture, tourism and external affairs, said: “This is an important bill that will enable questions on transgender status and history, and sexual orientation to be asked on a voluntary basis for the very first time, with no penalty for not answering them.

“It is widely accepted that there are currently data gaps on sexual orientation and trans status. Including questions on these demographics in the census will provide valuable data for public service planning purposes and will help public bodies meet duties under the Equality Act 2010.”