Taxi drivers in Bulgaria have vowed to start mass demonstrations unless Uber Bulgaria is banned from operating, an open letter of a trade union reads.

According to the Union Taxi, the company, which has been active in Bulgaria (mostly in the capital capital Sofia) since December of last year, is violating the country's legislation.

Representatives have argued Uber is are engaged in unfair competition and its transport services do not meet the legal criteria, since there are no licenses and documents for the drivers.

The document has been sent to the Competition Protection Commission (CPC), which according to the letter has been kept informed on the issue since December.

Another target of taxi drivers' demands is the Bulgarian mobile app Taxi Stars, which offers similar services to those of Uber and which, in the drivers' words, is also carrying out "illegal transportation of passengers."

Uber customers generally pay less than those of the "ordinary" taxi companies.

Anyone could easily become a Uber driver. There three simple requirements - the driver must have had a driving license for at least three years, and a car with no more than 10 years on the road. Additionally, Uber officially requests a driving record from the local Road Police Office to reaffirm suitability.

Uber cars, however, are never registered as transportation vehicles. The registration for the service is done online and the payments are also made through the credit or debit cards of customers.

Under Bulgarian law, one has to be registered in order to offer paid transport services. Cars used by Uber drivers cannot be legally subject to the inspections that the automotive administration conducts on taxi vehicles unless there are witnesses that the given vehicle has been involved in paid transportation.