If you have a problem with a taxi or minicab driver's behaviour, or you believe a vehicle to be unlicensed, report it immediately. Be sure to take down the vehicle licence number (printed on the number plate or disc) and the driver's licence number (normally shown on their badge).
For taxis, report your complaint directly to the body of authority, either the Public Carriage Office (PCO) in London or your local authority (your local council can give you details) outside London.
For private hire vehicles, or minicabs, you can try to resolve the complaint through the operating company. If you are not happy with the outcome or you feel your complaint is more serious then:
If the behaviour involves a criminal act, then you should also report it to the police. In an emergency call 999.