The Westminster government could torpedo a law passed in Scotland which would allow children to change their gender from the age of 16 as soon as today.
The Gender Recognition Reform (Scotland) Bill was passed by a majority of MSPs last month.
The bill would remove the need for a medical diagnosis of gender dysphoria for a gender recognition certificate, and reduce the time an applicant needs to live in their acquired gender.
Currently, someone looking to change their legal gender in the UK must live in their acquired gender for two years and get a diagnosis of gender dysphoria.
Under the powers in the Scotland Act 1998, which created the Holyrood parliament, prime minister Rishi Sunak and Scotland secretary Alister Jack could stop the bill from coming into law.
The Financial Times cited three people who are close to discussions on the issue in No 10 as saying Mr Sunak will now move to block the bill.
According to the report, ministers are set to review legal advice on the proposals today which states that the laws would have an impact on UK equalities legislation.
The prime minister has until Wednesday to make a final decision on whether to block the laws.
The Scottish government, led by the SNP’s Nicola Sturgeon, has insisted that the bill does not undermine any aspect of the UK-wide Equality Act. Ms Sturgeon argues that the new system does not afford any additional rights to anyone who gets a gender recognition certificate that they can’t already enjoy today.
On Friday, Sunak told BBC Scotland that his main concern was the bill’s impact across the UK, saying it was “completely standard practice” to look at the effect legislation passed at Holyrood could have.
Vice-chair of the Conservative party, Rachel Maclean also told the BBC: “We want to be compassionate to people who feel that they want to change their sex and their legal gender, but at the same time we have to make sure that we protect particularly single-sex spaces for women.
“They are there for a reason – to protect those vulnerable women and girls.”
Speaking on Sunday, Labour leader Sir Keir Starmer said he has “concerns” over the proposed changes because he considers 16 to be too young to decide to change gender.
Sir Keir told the BBC’s Sunday With Laura Kuenssberg programme: “I have concerns about the provision in Scotland, in particular the age reduction to 16 and in particular the rejection of our amendment in relation to the Equalities Act.”
Pressed on whether he thinks someone of 16 is old enough to decide to change their gender, he replied: “No, I don’t think you are.”
He added that Labour’s position is to “modernise the legislation to take out the indignities” for trans people legally changing gender.
Also speaking on Sunday, transport secretary Mark Harper said ministers are awaiting “detailed analysis” of how Scotland’s gender law will affect UK legislation, such as the Equalities Act.
He told the BBC: “We are not proposing to make those changes for England, but what we have to do is make a decision about whether that legislation impacts on legislation elsewhere in the UK.
“One of those pieces of legislation is the Equalities Act.
“That is why we need a detailed analysis of that, and that is the information the Government needs before it can take a decision.”
Stephen Flynn, the SNP’s Westminster leader, said it would be an “outrage” if London did choose to intervene, saying it would amount to the UK Parliament “overstepping massively”.
“What we have is a right-wing UK Conservative Government which is seeking to roll back on the democratic powers of the Scottish Parliament – that’s an outrage”.