Almost 90 per cent of sexual assaults, harassment and voyeurism in swimming pool and sports centre changing areas happen in unisex facilities.
The Sunday Times reported that in 2017-18 there had been 120 complaints arising from unisex changing rooms, compared to 14 for single-sex facilities.
This is despite unisex changing rooms being less common than single-sex facilities.
Gender-neutral changing facilities are on the rise as councils seek to cater for transgender people.
The Government is proposing to change the Gender Recognition Act to make it easier for a man to legally become a woman and vice versa. This could include allowing people to ‘change sex’ simply by declaring it.
But campaigners say ‘self-declaration’ would endanger women and girls, with some feminists warning it would turn every female facility into a unisex space.
They say any man would be able to gain access to all-female spaces by simply ‘self-identifying’ as a woman.
MP for Monmouth David Davies said introducing self-declaration would be “wrong and dangerous”.
He said: “These figures show that women and girls are more vulnerable in mixed changing rooms and there is a danger these places are becoming a magnet for sexual offenders.
“It simply doesn’t make sense to enable men to have greater access to women’s spaces.”
While transgender activist Paris Lees denied there had been any problems, Nicola Williams, spokeswoman for Fair Play for Women, said that changing areas should be single-sex “as a matter of course”.
She added: “This is obvious, elementary safeguarding.”