DATA experts were left out of early talks on sex and gender census questions, documents show.

The progress of legislation on the vital survey, which included a public consultation, has been marked by fierce debate between some women’s groups and transgender organisations on the way the data is collected.

While transgender groups say the people they represent must not be required to answer in accordance with their biological sex, opponents like For Women Scotland say failure to collect this data could skew service provision and threaten provisions for females.

Though the Scottish Parliament has voted to include a mandatory male-female sex question and voluntary transgender status section, final guidance on the census has yet to be approved and calls from both sides continue.

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A three-day protest was held at Holyrood by the Scottish Trans Alliance (STA) earlier this month.

It comes months after the Parliament’s cross-party Culture, Tourism and External Affairs Committee raised concerns about the way work on the census had been conducted, citing a lack of consultation with women’s groups, language conflating sex and gender, and a lack of definition around gender identity.

Now a Freedom of Information Request indicates that officials did not meet with independent statisticians or other users of census data in the early question development phase.

Responding to the inquiry, government body National Records of Scotland identified meetings between officials and groups advocating change, including Equality Network, STA, Stonewall Scotland and LGBT Health prior to the introduction of draft legislation. No such meetings with statisticians were identified.

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However, the response did include a list of talks with a wider range of groups in recent months.

Edinburgh-based policy analysis collective Murray Blackburn Mackenzie (MBM), which is critical of gender self-identification in the census, said the Scottish Government “needs to engage more fully” with researchers and those who use census data.

In a blog post, the organisation linked the issue to the consideration of changes to the Gender Recognition Act. That was put on hold in the summer, though Equalities Secretary Shirley-Ann Somerville said the SNP administration “remains committed” to reform.

MBM said: “The census is not the appropriate vehicle to either pre-empt legal reform on gender self-identification, or to set legal precedents.

“If we lose count of sex as a biological category, we will also lose our ability to chart and address sex-based discrimination.”

STA’s James Morton said the mandatory sex question could threaten trans equality in “our use of services including the NHS and education”.