The UK government may seek to block Scottish reforms making it easier for people to change gender.
It comes after the Scottish Parliament voted to lower the age when people can apply to change their legal gender to 16, and remove the need for a medical diagnosis of gender dysphoria.
But this has prompted a clash with the UK government who have concerns over safety for women and children.
Nicola Sturgeon’s Scottish government says it will fight attempts to stop it.
On Thursday, members of the Scottish Parliament (MSPs) voted by 86 votes to 39 to approve the controversial self-identification system, which makes it easier for people to obtain a gender recognition certification (GRC).
The UK government could prevent the legislation becoming law by blocking Royal Assent – when the Bill gets formal agreement by the King and becomes an Act of the Scottish Parliament. It has also not ruled out mounting a legal challenge.
UK Minister for Women and Equalities Kemi Badenoch said the Scottish government has not addressed the implications of the bill on the lives of women and girls.
She said in a statement: “The UK government is now looking at provisions that can prompt reconsideration and allow MSPs to address these issues.”
Scottish Secretary Alister Jack warned: “We will look closely at that, and also the ramifications for the 2010 Equality Act and other UK-wide legislation, in the coming weeks – up to and including a Section 35 order stopping the Bill going for Royal Assent if necessary.”
Under UK law, it can apply to have Scottish laws struck down by arguing they would conflict with UK-wide equalities legislation. This power has not been used before.
But a spokesman for the Scottish government warned that any attempt by the UK “to undermine the democratic will of the Scottish Parliament will be vigorously contested”.
Scotland’s Social Justice Secretary Shona Robison, responding to Mr Jack, said: “It would be very disappointing if the UK government didn’t respect Scottish democracy and the decision of the Scottish Parliament.
“This area of policy is entirely within devolved competence.”
Previously, Ms Sturgeon said she would “never apologise for trying to spread equality, not reduce it, in our country”.
The Gender Recognition Reform (Scotland) Bill’s opponents, including nine SNP MSPs who voted against it, have fears over its potential impact on women and girls, in particular single-sex spaces, like toilets.
The Scottish government insists little will change and exceptions barring trans people from single-sex space in some circumstances in the Equality Act will stand.
People in Scotland have been able to change their legal gender from male to female or female to male since 2005.
The Scottish government believes the existing process can be intrusive and distressing and put people off applying for a Gender Recognition Certificate.
The new rules, which are expected to come into force some time next year, will mean applicants will now only need to have lived in their acquired gender for three months – or six months if they are aged 16 and 17 – rather than two years.
There will be also be a three-month “reflection period” during which they can change their minds and it will be a criminal offence to make a false declaration or false application for a GRC, with anyone who does so potentially facing up to two years in prison.
It will be possible to de-transition by going through the process again.
Nine other European countries have already adopted self-declaration systems for legal gender recognition, including the Irish Republic, Denmark, Norway, Portugal and Switzerland.
Also on Thursday, Spain passed a bill bringing it a step closer to allowing people to change their officially registered gender by filling in a form.
Source: BBC