Some 16,500 illegal fatbikes made in China have been impounded in the last seven weeks alone, the enviroment and transport inspectorate ILT has said.

A great number of the bikes were intercepted in the port of Rotterdam and around one thousand were located at distribution centres belonging to a Dutch retailer.

The fatbikes are illegal because they can be made to reach speeds of up to 45 kph by using a simple code or app. The legal maximum speed for electric bikes is 25 kph.

Often the bikes are already fitted with a much too powerful motor and other technical qualities which turn them into de facto motorcycles. However, the frame, brakes and tires have not been tested for higher speeds, the ILT said, putting riders at risk of serious accidents and injury.

The ILT said a growing number of cheap, unsafe and untested motorcycles posing as fatbikes are being imported. “The only way to combat this is to ban the sale of these bikes via the official trading channels,” it said.

There is mounting concern about the surge in accidents involving fatbikes. In 2022, just seven fat bike riders ended up in hospital emergency departments, but last year that had soared to 59. In the first four months of this year, there were 33 hospitalisations, a trend which if continued would take the full year total to around 100.

The debate around new rules for fatbike riders is ongoing, with most MPs wanting to introduce a minimum age and helmet wearing. Infrastructure minister Barry Madlener recently reiterated there are major problems in developing special traffic laws for fatbikes and it would “not be useful” to do so, despite parliament’s calls for action.