Spain’s competition watchdog has fined online reservation group Booking.com €413.2 million for abusing its dominant market position in the country for the last five years.

The fine, in two parts, is the biggest ever claimed by the CNMC, according to AFP.

The agency said Amsterdam-based Booking.com had been taking advantage of its dominant market share to impose unfair conditions on hotels, and had restricted competition. Booking.com is said to control between 70% and 90% of the Dutch online holiday booking market.

The CNMC also said that Booking.com forces Spanish hotels to sue in the Netherlands in cases of conflict and to use Dutch law, “which leads to unequal litigation costs”.

The case against Booking.com was brought by the Spanish hotel industry.

Parent company Booking Holdings said it plans to appeal against the fines as it strongly disagrees with the results of the investigation.