Almost 1,000 minicab drivers are said to have joined a protest against congestion charges they claim will cut their take-home pay by up to 25%.
The demonstration in central London on Monday was called by the Independent Workers Union of Great Britain which claims the charge is a "tax on the poor" and will do little to reduce congestion in the capital.
The daily charge of £11.50 will have to be paid by private hire drivers, such as those working for Uber, from April.
The union said roads outside Transport for London's offices were blocked by the demonstration, which it vowed to repeat every Monday.
Spokesman James Farrar said the protest showed how angry drivers were about the extension of the congestion charge.