Online taxi company Uber will have to pay €50,000 for breaking the terms of a court ruling and continuing to offer unlicenced taxis, Dutch transport ministry inspectors said at the weekend.

Ministry inspectors tracked down four drivers in Amsterdam and one in Rotterdam who were working for Uber, the Financieele Dagblad reported. They were all given a formal warning and told they would have to pay €10,000 if found breaking the taxi rules again.

Uber was banned from offering its budget service Uberpop in the Netherlands in December. The company was told then if any more people were found driving on behalf of Uberpop, it would have to pay a fine of €10,000 per driver.

Uberpop drivers are breaking Dutch rules which say all taxi drivers have to have a licence and proper insurance. Licenced taxi drivers in both Amsterdam and Rotterdam have called on the authorities to get tough on Uber for flouting the regulations.

Last time Uberpop drivers were fined, the US company said it would pick up the bill. Last week the company said it was cutting fees for Uberpop taxis by 15%.

Uber is reported to have raised $1.2bn from investors in December 2014, valuing the company at over $40bn.