A judge has upheld a decision to allow transgender people in Scotland to choose which sex they want to identify as in the upcoming census.

National Records for Scotland will ask Scots 'what is your sex?', offering the options of male or female, but accompanying guidance says that respondents can answer according to their own preference. 

"If you are transgender, the answer you give can be different from what is on your birth certificate. You do not need a gender recognition certificate," the guidance reads.

Lord Sandison threw out a legal challenge against self-identification brought by feminist group Fair Play for Women. 

He wrote, "In the modern age, where social change has meant that such issues are much more openly and widely discussed and debated, I would find it impossible to find that the word 'sex' in a statute enabling the general population to be asked questions for the wide and general purposes for which a census is conducted falls to be regarded as restricted in the sense for which the petitioner contends.

"Rather, I would accept the suggestion that biological sex, sex recognised by law, or self-identified (or 'lived') sex as at the date of the census are all capable of being comprehended within the word."

The census is taking place on 20 March and will involve around 2.5 million Scottish households. 

Fair Play for Women said it was disappointed by the ruling and plans to appeal.

"The guidance proposed for the sex question will jeopardise the collection of accurate data on sex in the Scottish census and erodes the harmonisation of data collected via censuses across the UK," the group said.