Copenhagen - Denmark's national transport authority filed a police complaint on Wednesday against the Uber car-sharing startup which they said was operating illegally.
"We don't think their services are in line with the law, so we have asked the police to look into it," Mads Gundelund Gerlach a spokesman for the Danish transport authority told AFP.
The complaint was directed at the newly launched Uber Black - a luxury car service which the Uber website says is only available in Copenhagen - and the yet to be launched cheaper UberPOP service.
"They haven't made any contact with us," said Gerlach, explaining that the company had not been granted a permit to operate.
Founded in 2009, the San Francisco-based firm - which lets customers hail cars and pay for their journey via Uber's smartphone app - is now present in more than 200 cities in 45 countries.
The app uses GPS to put customers in contact with the nearest driver and Uber charges a commission for each journey.
Taxi companies across Europe and the United States have protested that Uber taxis do not use meters or follow the same regulations that apply to them.
Germany temporarily banned the service in August and a court in Paris ordered the company to pay €100 000 in damages for presenting a paid transport service as carpooling.