Barcelona’s new mayor is picking a fight with home rental websites as she tries to crack down on uncontrolled tourism that she fears could drive out poor residents and spoil the Catalan capital’s charm.

Ada Colau is threatening to fine firms like Airbnb and Booking.com if they market apartments from tourists without a number showing that they are on the Catalan tourism register.

Colau, a left-wing former housing activist elected in May, also wants rental websites to hand over information on the property owners.

“Everybody must comply with the same game rules,” Colau told Reuters in Barcelona’s city hall.

“An internet platform cannot become a means to thwart the regulations and to shelter illegal tourist apartments. In that case we do have to intervene very forcefully.”

Colau, who headed a coalition backed by Spanish anti-austerity party Podemos, is one of a new breed of local politicians who have come to power amid a backlash against traditional parties.

The dispute with rental websites is an example of the friction created by the new online “sharing economy”, ranging from San Francisco and Santa Monica restricting short-term home rentals to court injunctions that have hit online taxi service Uber in a number of countries.

San Francisco-based Airbnb, which matches people wishing to rent out their homes or rooms to temporary guests, has been one of the fastest-growing start-ups of recent years and is valued at more than $20 billion.

Airbnb, which has around 18,600 listings in Barcelona, its third highest number in Europe, said property owners could add the tourism registry number to their listing and said its users must comply with local rules.

An Airbnb spokesman, asked if it would hand over owners’ information to city hall, said it would not do so voluntarily.

Booking.com, operated by Priceline Group Inc, said it had “stringent measures in place” to make sure all its properties around the world complied with local laws.

Tourism Surges

Since hosting the Olympic Games in 1992, Barcelona has seen a stratospheric increase in tourists, ranging from weekend hen parties to cruise ship visitors to culture vultures on the trail of Picasso paintings or the buildings of Gaudi.

Tourism provides nearly 400,000 jobs in Catalonia, 13 percent of the total, and it makes up 12 percent of Barcelona’s economic output.

But with 27 million visitors descending on the city of 1.6 million last year, the procession of tourists flowing down Las Ramblas, Barcelona’s most famous street, through the old town and the port lined with luxury yachts is becoming too much for some local people.

Residents of La Barceloneta, a working-class neighborhood next to the beach, hold regular demonstrations to protest against the growing pressure from tourism and tourists’ bad behavior, which they say includes drunkenness, urinating in the streets and partying until the small hours.

One target of their anger is the sharp increase in people letting out rooms or apartments using web sites such as Airbnb.

“The tourist flats are making the area much more expensive. Flats that could perfectly well be rented for 300 or 400 euros (a month) are being rented for 600 or 700,” said Oriol Casabella, spokesman for a La Barceloneta neighborhood group.

“If this doesn’t stop, a time will come when they will throw us out because there are many people who can’t afford these flats,” he told Reuters.

It is not the first problem Airbnb has had in the region. In July 2014, the Catalan regional government fined Airbnb 30,000 euros ($35,000) for breaking rules on people letting individual rooms in their homes and threatened to block access to its website from Catalonia if Airbnb did not change its ways.

Colau says there are thousands of unlicensed apartments in Barcelona that are not paying the Catalan tourist tax of 0.65 euro ($0.76) per person, per night.

Soon after she took office, the council froze new licences for hotels and other tourist accommodation in Barcelona for up to a year.

The council will use that time to draw up a new plan for tourism and to see “if there is still room for growth or if it is time to stabilize the number of visitors,” Colau said.

For years before the freeze, new tourist apartments were banned in the old part of town.

The Airbnb spokesman said the rules being applied to home sharing in Barcelona were designed for a different era.

“Barcelona should be introducing smart policies to support local residents – not acting against them,” he said.

(Additional reporting by Silvio Castellanos; Editing by Angus MacSwan)