Carmena gave her approval of an idea of a “no swimsuit day” in the city's municipal swimming pools after a petition was lodged by nudist groups.
She informed the different districts of Madrid of the plan in a statement sent out by email on Monday, reported El País.
In the email, sent by the city's department of Culture and Sport, the mayor writes that, if they think it appropriate, local districts should fix a date to celebrate no swimsuit day.
The initiative comes after a petition was lodged by the Association for the Development of Nudism (AND), championing the right of people to practice nudism in public places.
“What we want to do with this day is to educate and transmit our values, which are Western values,” AND president Ismael Rodrigo told El País.
“There is nothing criminal about the body and the best way we can show that is to try not to wear clothes when it's not necessary, and in the pool, it isn't,” he added.
Carmena wrote that there would be signs at the entrances to the public swimming pools informing people that it was no swimsuit day in case parents preferred not to take their children.
Children would be allowed, however, as long as they were accompanied by an adult.
The contents of the email were revealed by conservative Popular Party politician, Esperanza Aguirre, a long-time critic of Carmena, to whom she lost the mayoral race in 2015.
“I don't know if you have the courage to implement a no veil day for Muslim women as well,” she said.
Aguirre said Madrid's left-wing council “only does slogans” and the idea of having a no swimsuit day was just one more of Carmena's “crazy ideas”.
Madrid's City Hall pointed out in a statement on Tuesday that it had not authorized the day, but given individual districts the chance to decide for themselves. It added that the day would probably be "towards the end of August".
It is not the first time Carmena, Madrid's first left-wing mayor in 24 years, has championed nudism. In 2015 she designated September 6th as “no swimsuit day”, but the day was only celebrated in one public swimming pool in Madrid located in the Casa de Campo.
If Carmena's plan goes through this year, many more public swimming pools could join in the celebration of no swimsuit day.