Nicola Sturgeon

Scottish Secretary Alister Jack said he would use section 35 following a review of the bill by UK government lawyers. UK ministers are concerned the bill will have an “adverse impact” on the Great Britain-wide equalities regime.

Sources have said that blocking it would safeguard the devolution settlement and denied claims that they were trying to inflame tensions as part of a culture war.

Mr Jack said: “After thorough and careful consideration of all the relevant advice and the policy implications, I am concerned that this legislation would have an adverse impact on the operation of Great Britain-wide equalities legislation.

“Transgender people who are going through the process to change their legal sex deserve our respect, support and understanding. My decision today is about the legislation’s consequences for the operation of GB-wide equalities protections and other reserved matters.

“I have not taken this decision lightly. The Bill would have a significant impact on, amongst other things, GB-wide equalities matters in Scotland, England and Wales. I have concluded, therefore, that this is the necessary and correct course of action.”

First Minister Nicola Sturgeon said her government would likely seek judicial review of the decision, saying the use of section 35 would create a “very, very slippery slope indeed”.

Ms Sturgeon tweeted: “This is a full-frontal attack on our democratically elected Scottish Parliament and its ability to make its own decisions on devolved matters.”

The law was passed at Holyrood by 86 votes to 39 and received the overwhelming support of the SNP, Labour, the Greens and the Lib Dems in December, following years of consultation and debate.