While the opinion of the Advocate General is non-binding, a ruling by the European Court of Justice would mean EU member states can regulate Uber and other such companies as a transport rather than "information society" business.
Ride-hailing app Uber may be a pioneer in its field but at heart it is an ordinary taxi company and should be regulated as such, a top EU lawyer said Thursday.
Uber claims it is a service provider, connecting riders with freelance drivers directly and much more cheaply than traditional cab companies.
It has run into huge opposition from critics and competitors who say this allows it to dodge costly regulation such as licencing requirements for drivers and vehicles.
In an opinion on a case brought by a taxi drivers association in the Spanish city of Barcelona, Advocate General Maciej Szpunar of the European Court of Justice (ECJ) said San Francisco-based Uber should be treated as a traditional taxi company.
"The Uber electronic platform, whilst innovative, falls within the field of transport," Szpunar said in an ECJ statement.
"Uber can thus be required to obtain the necessary licences and authorisations under national law," he said.
The ECJ's advocate generals are senior lawyers whose opinion the EU's top court very often follows when it comes to a final ruling.
Early last year, Uber decided to only operate a limited a version of its UberX service in Spain, which uses licenced, professional drivers instead of amateurs.
The company does not employ drivers or own vehicles, but instead uses private contractors with their own cars, allowing them to run their own businesses.
Licenced taxis must undergo hundreds of hours of training and they accuse Uber of endangering their jobs by using cheaper drivers who only need a GPS to get around.
Szpunar said he was of the opinion that Uber could not be considered to be solely an information service which falls under a different regulatory regime, but rather it was a composite service, providing both information electronically and more importantly transport.
"Uber cannot be regarded as a mere intermediary between drivers and passengers," Szpunar said.
Since the transport component is the main part of its offering, Uber "must be classified as a 'service in the field of transport.'"
He said that, on that basis, "it is thus subject to the conditions under which non-resident carriers may operate transport services within member states. In this case, possession of the licences and authorisations required by the city of Barcelona regulations."