Uber has lost its London licence after a series of safety passengers alarms.
Transport for London (TfL) said it has identified “a pattern of failures” by the taxi app firm.
It decided Uber is “is not fit and proper at this time”.
Uber said the decision was “extraordinary and wrong” and would challenge it.
It has 21 days to appeal, during which time it can continue to work.
TfL said an Uber computer system failing allowed unauthorised drivers to upload their photos to other legitimate Uber driver accounts.
More than 14,000 trips were erroneously booked – all of them insured.
Another breach allowed dismissed or suspended drivers to create an Uber account and carry passengers.
Helen Chapman, of TfL, said:
“As the regulator of private hire services in London we are required to make a decision today on whether Uber is fit and proper to hold a licence. Safety is our absolute top priority.
“While we recognise Uber has made improvements, it is unacceptable that Uber has allowed passengers to get into minicabs with drivers who are potentially unlicensed and uninsured.
“It is clearly concerning that these issues arose, but it is also concerning that we cannot be confident that similar issues won’t happen again in future.
“If they choose to appeal, Uber will have the opportunity to publicly demonstrate to a magistrate whether it has put in place sufficient measures to ensure potential safety risks to passengers are eliminated.
“If they do appeal, Uber can continue to operate, and we will closely scrutinise the company to ensure the management has robust controls in place to ensure safety is not compromised during any changes to the app.”
Jamie Heywood, of Uber, said: “TfL’s decision not to renew Uber’s licence in London is extraordinary and wrong, and we will appeal.
“We have fundamentally changed our business over the last two years and are setting the standard on safety. TfL found us to be a fit and proper operator just two months ago, and we continue to go above and beyond.
“On behalf of the 3.5 million riders and 45,000 licensed drivers who depend on Uber in London, we will continue to operate as normal and will do everything we can to work with TfL to resolve this situation.”
