Campaigners have warned that Marks & Spencer's policy of allowing men who identify as women to use female changing rooms, is putting women and girls at risk of voyeurism.
The Mail on Sunday reported that the retailer has faced protests from customers for allowing anyone who describes themselves as a woman to use its female changing rooms.
A Lib Dem peer who advocates single-sex spaces, Baroness Emma Nicholson, stated that, "since changing of clothes can lead to voyeurism, newer legislation (the upskirting law) calls this laxness of provision into question," in a letter to Archie Norman, the retailer's chairman.
She also cautioned that the retailer is putting women and girls are risk of being spied on and photographed by sexual predators by allowing anyone who says they are a woman to enter female changing areas.
Ms Nicholson warned Mr Norman that the retailer's position is at odds with the law after Liz Truss the Equalities Minister said that, because of concerns they may threaten women's rights, the Government was rejecting "trans-inclusive" policies.
M&S said it had assured Baroness Nicholson that its fitting rooms provide private and secure spaces, with individual lockable cubicles. The supermarket has defended its practice, asserting that "as an exclusive retailer and in line with most other retailers, we allow customers the choice of fitting room in respect of how they identify themselves.
In a letter published by her office Baroness Nicholson said, "I will ensure that government guidance gives a clear message to service providers, schools and others, putting their ability to provide single-sex spaces beyond doubt." and has made clear that service providers and shops and are legally entitled to deny male-born people access to female spaces, and plans to issue new guidance.
Ms Truss claimed that M&S had "misunderstood" the law on equality and single sex space.
Mandy Peters Solicitors
Lewisham
020 8297 4414