Barcelona's Mayor Ada Colau. MARTA PÉREZ / EFE

Airbnb said it was saddened by the decision and would appeal. “Barcelona is the only city in the world to have fined us,” noted Airbnb in a statement on its website, adding: “Barcelona is going in the opposite direction to the majority of cities in Europe and the world, and unlike those cities, has shown no real interest in exploring a constructive dialogue with Airbnb in recent months.”

“Less than a month ago we met with officials and Airbnb committed to work together in the best interests of the city. Airbnb is part of the solution in Barcelona,” the Catalan division of Airbnb said in the statement released on Thursday.

It is not the first time the city has fined San Francisco-based Airbnb, one of the fastest-growing start-ups of the so-called sharing economy valued at around $25 billion.

Barcelona City Hall reported that Airbnb and Homeaway were repeat offenders, and were both fined €30,000 in August for failing to follow regional tourism laws. Homeaway paid the fine, while Airbnb appealed against it but both continued to publicize unlicensed apartments said left-wing Mayor Ada Colau justifying her decision to impose the new €600,000 fines.

Airbnb is blamed for pushing up rents and depriving locals of accommodation

Colau, who took over in June 2015, has frozen the granting of new tourist licenses for homes and hotels, and this summer launched a plan to stop people from letting out their homes without a license via homesharing websites.

She has blamed the sharp rise in Airbnb’s popularity for tension among residents who fear an increase in ‘binge tourism’ and have protested against rowdy visitors. The number of people using Airbnb in Barcelona has tripled to 900,000 in the three years prior to 2015, its own data shows.

Barcelona City Hall has now created a multi-lingual website that invites residents to identify and report unlicensed tourist accommodation, along with a free telephone number allowing locals to expose neighbors that break the rules.

Barcelona City Hall reported that Airbnb and Homeaway were repeat offenders

Owners who wish to rent out property to tourists must apply for a license and display it on any online advertisement. A team of 20 inspectors set up by city hall is tasked with rooting out those who do not obey the new rules.

“It shouldn’t be possible that thousands of apartments are operating without a license, illegally, without paying tax and at the peril of neighboring residents,” Colau said on a local radio station on Thursday after the fine was announced by the Catalan regional government.

A growing number of European cities, among them Berlin, Paris and Barcelona say home-sharing websites for tourists deprive locals of apartments for permanent rental and push up prices for homes remaining on the market. Barcelona has seen a surge in tourism and attracts around 7 million visitors a year.

A report published in September by Barcelona City Hall showed found that nearly 40% of homeshare lets were unlicensed, saying that the practice was reducing the quantity of apartments on the market and driving rents up.

The report also said almost 8% of the city’s total rental accommodation is now made up of tourist appartments. Owners of these properties earn 2.3 times to 4 times more than they would do so through convential rental arrangments, the study added

But Airbnb this week described the situation in Barcelona as “contradictory.”

“It favors commercial operators and apartments used only for tourism in tourist areas to the detriment of people who want to share their home,” said the firm, noting that many families housed tourists to supplement their income.