Private ride-hire service Uber has been suspended in London by the city’s transport regulatory body, Transport For London.
TfL concluded the ride-hailing app firm was not fit and proper to hold a London private hire operator licence.
It said it took the decision on the grounds of “public safety and security implications”.
TfL’s concerns include Uber’s approach to carrying out background checks on drivers and reporting serious criminal offences.
The current licence expires on 30 September but Uber has 21 days to appeal and can continue to operate until that process expires.
Mayor of London Sadiq Khan said in a statement: “I fully support TfL’s decision – it would be wrong if TfL continued to license Uber if there is any way that this could pose a threat to Londoners’ safety and security.
“Any operator of private hire services in London needs to play by the rules.”
Confirming it would appeal against the decision, Uber said it showed the world “far from being open, London is closed to innovative companies”.
The company said: “Transport for London and the mayor have caved in to a small number of people who want to restrict consumer choice.”
“3.5 million Londoners who use our app, and more than 40,000 licensed drivers who rely on Uber to make a living, will be astounded by this decision,” the company added.
Uber’s general manager in London Tom Elvidge said: “To defend the livelihoods of all those drivers, and the consumer choice of millions of Londoners who use our app, we intend to immediately challenge this in the courts.”