Irish low-budget airline Ryanair has been fined 370,000 euros by the Netherlands Consumer Authority for hidden costs associated with tickets purchased online by Dutch travellers.

The watchdog said that European regulations had been violated because full costs were unclear, consumers were not given the option to correct mistakes before finalising a booking and the company was difficult to contact and provided information in English, not Dutch.

"Ryanair offered air fares on its website that did not include all foreseeable and unavoidable costs, such as fees and surcharges," it said. "Consumers thus paid considerably more than the air fares that were initially displayed."

Ryanair, which the authority said has since revised the booking process and now provides accurate prices in advertisements, said it will appeal against the ruling.

"The decision of the Dutch consumer authority is littered with errors. Ryanair will appeal this unfounded decision and confirms that its website fully complies with all EU and Dutch consumer protection regulations," a Ryanair spokesman said in a statement.