The United Nations has criticised Nicola Sturgeon over her gender reform plans for teenagers - saying they could put the safety of women at risk.
Reem Alsalem, the UN's special rapporteur on violence against women and girls, said the proposals could "open the door for violent males who identify as men to abuse the process".
In a letter to James Cleverly, the Foreign Secretary, she said the Scottish government's plans lacked "clarity" on how people applying to change gender would be checked.
And she added: "Simplifying and fast-tracking the procedure does not necessarily make it fairer or more efficient."
Ms Alsalem said she was concerned that violent men could abuse the self-identification process, putting at risk the safety of women.
"I share the concern that such proposals would potentially open the door for violent males who identify as men to abuse the process of acquiring a gender certificate and the rights that are associated with it," she wrote.
"This presents potential risks to the safety of women in all their diversity (including women born female, transwomen, and gender non-conforming women)."
Level of scrutiny not laid out
Ms Sturgeon's Gender Reform Recognition Bill would allow children as young as 16 to apply to change their gender without medical checks.
The legislation also slashes the amount of time an individual has to live in their "acquired gender" from two years to three months before they receive a Gender Recognition Certificate. An additional three-month "reflection" period is also mandatory for all applicants.
Campaigners worry this could mean biological males joining all-girl sixth forms and Scottish biologically male prisoners moving into female prisons.
It is understood that Kemi Badenoch, the Equality Minister, has concerns about Ms Sturgeon's proposed approach.
In her letter, Ms Alsalem wrote that there was "insufficient clarity in the proposed self-identification procedure".
"Currently, the Scottish government does not spell out how the government will ensure a level of scrutiny for the applications made to acquire a gender recognition certificate under the new proposal," she said.
"It is not unreasonable to expect the government to spell out what level of scrutiny will continue in the procedure, or detail important aspects of it, including the specific steps the procedure entails and the conditions for refusing such applications.
"Other governments that have adopted a self-identification procedure for the legal recognition of a gender identity have done so. Simplifying and fast-tracking the procedure does not necessarily make it fairer or more efficient."
'No safeguarding measures'
She pointed out that MPs had previously called for "robust guidance" on how a system of self-declaration would work in practice, ensuring that male prisoners with a record of sexual assault or domestic violence, who self-identify as a woman, should not be transferred to a woman's prison.
Ms Alsalem added: "The ongoing efforts to reform existing legislation by the Scottish government do not sufficiently take into consideration the specific needs of women and girls in all their diversity, particularly those at risk of male violence and those who have experienced male violence.
"It does not provide for any safeguarding measures to ensure that the procedure is not, as far as can be reasonably assured, abused by sexual predators and other perpetrators of violence. These include access to both single-sex spaces and gender-based spaces."
She added: "It is important to note that insistence on safeguarding and risk management protocols does not arise from the belief that transgender people represent a safeguarding threat.
"It is instead based on empirical evidence that demonstrates that the majority of sex offenders are male, and that persistent sex offenders will go to great lengths to gain access to those they wish to abuse. One way they can do this is by abusing the process to access single-sex spaces or to take up roles which are normally reserved to women for safeguarding reasons."
'Funding must be ringfenced'
The special rapporteur said she had been made aware of reports that "indicate a failure to provide single-sex spaces to female survivors of male violence, who, because of their experiences, do not feel able to access a trans-inclusive service, leading to their self-exclusion from support and refuge services".
"It is vital that service providers in Scotland continue to be able to provide both single-sex and gender-based services, and funding must be ringfenced for a certain proportion to be single sex, balancing the needs of the different demographics without placing them in conflict."
She concluded: "While I commend the [Scottish] government for listening to the voices of transwomen, including organisations that represent them, I am concerned that the consultations for this proposal do not appear to have been sufficiently inclusive of other groups of women, most notably female victims of violence.
"It has been reported that five survivors of male violence approached the Scottish Parliament's equalities, human rights and civil justice committee to speak in a private session about their concerns in relation to the Bill and their own experiences of self-exclusion.
"The convenor reportedly informed the group that the Committee did not have time to see them and to put their objections in writing."