In its assessment of the EHRC guidance, Sex Matters took issue with the following phrase: "It is unlikely to be either practical or appropriate to approach any particular individual to make enquiries about their sex in relation to facilities, such as toilets, which are incidental to the primary service.”
The sex-based rights group responded in a publication entitled <a class="break-all" href="https://archive.is/o/lLjDq/sex-matters.org/posts/updates/sex-is-not-special-category-data/?ref=ed_latest" rel="nofollow" target="_blank">"Sex is not a 'special category' data", saying: "There is no legal basis for this instruction, which in effect licenses men to enter women’s facilities and claim that it is inappropriate, possibly unlawful and a breach of their human rights to challenge them."
The group further stated: "Telling staff supervising single-sex spaces that they must second-guess themselves when they become aware of a man engaging in the deviant behaviour of accessing a female-only space, or risk breaching data-protection law, will lead to unwanted conduct related to the protected characteristic of sex that is likely to meet the definition of harassment in the Equality Act. It 'violates a person’s dignity or creates an intimidating, hostile, degrading, humiliating, or offensive environment'."
From article at https://www.thenational.scot/news/26143769.good-law-project-report-sex-matters-deviant-remark/
and at https://archive.is/lLjDq