Among the many messages sent out by politicians during the UN Climate Conference in Copenhagen, “Be sustainable — don’t buy sex” has to be one of the least expected. This was the advice circulated by Ritt Bjeregaard, the city’s mayor and a former EU Environment Commissioner, sent via postcard to all the hotels in the city to tell them to stamp down on conference-goers looking to patronise prostitutes on their premises.

Prostitution is legal in Denmark (though brothels and pimping are not), and sex workers had been expecting to do a roaring trade during the two-week conference.

Mayor Bjeregaard’s note sparked an angry response from the Sex Workers Interest Group, which pointed out that its members are not breaking the law and promised free sex to any attendees who produced one of the postcards along with their conference accreditation.

“This is sheer discrimination. Ritt Bjerregaard is abusing her position as mayor in using power to prevent us carrying out our perfectly legal job. I don’t understand how she can be allowed to contact people in this way,” the group’s spokeswoman Susanne Møller told website avisen.dk.