"Predators" could exploit gender self-identification, government minister Kemi Badenoch has said, as she voiced her opposition to proposed reforms.
The minister for women and equalities argued that offenders would be able to "exploit any system that says you can just say you are what you are," putting women and girls at risk.
In an unprecedented move earlier this week, the UK government blocked legislation passed by the Scottish parliament to reform the gender recognition process.
It is the first time Westminster has used the power since devolution nearly 25 years ago.
The Gender Recognition Reform (Scotland) Bill was passed by a majority of MSPs last month, with Nicola Sturgeon hailing it as a "historic day for equality".
The bill would approve reforms allowing trans people to obtain a gender recognition certificate (GRC) without the need for a medical diagnosis.
The age someone can legally change their gender in Scotland would also be lowered to 16 from 18, and someone would only have to live in their acquired gender for three months - reduced from two years.
Ms Badenoch made her comments in an interview with The Times, highlighting what she sees as the risks of self-identification.
She told the newspaper: "We have no problem with that in the sense that we want people who are trans to be able to live their lives freely and as they wish.
"The problem is that self-identification also makes life a lot easier for other people we don't want to have those sorts of freedoms.
"Predators would be able to exploit any system that says you can just say you are what you are.
"It's also quite bad for trans people. They then get conflated and associated with the predators and people who are looking to do bad things.
"That's why having a stricter regime rather than a loose regime is quite important."
Ms Badenoch also hit out at the highly-charged emotions around the issue.
"Rather than having a disagreement on whether you think self-identification is okay or not okay, people who have a different view are then abused, insulted, called transphobic," she added.
"That's what has really toxified the debate and made a lot of people scared to say what they think."
Earlier this month, Ms Badenoch announced that the government would be updating the list of countries from which the UK will accept gender recognition certificates.
Currently, people who have already had their gender recognised in 41 overseas countries and territories can apply for a GRC in the UK through a simplified process.
Ms Badenoch said nations which no longer have "equivalently rigorous" systems to the UK will be removed from the list, meaning people from there would have to apply for a UK GRC through the main route.