Uber will not be issued a new private hire licence, Transport for London (TfL) has said.
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".
Confirming it would appeal against the decision, Uber said it showed the world "far from being open, London is closed to innovative companies".
TfL's concerns include Uber's approach to carrying out background checks on drivers and reporting serious criminal offences.
Uber's current licence is due to run until 30 September.
It has 21 days to appeal against TfL's decision and can continue to operate while any appeals are ongoing.
Some 3.5 million passengers and 40,000 drivers use the Uber app in London.
Mayor of London Sadiq Khan said: "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."
Fred Jones, head of cities for Uber across the UK and Ireland, told the BBC Uber drivers had to pass the same safety checks as black cab and mini cab drivers in London.
There had been growing speculation that the app could be banned from London.
Opponents of the firm claim it causes gridlocked roads and does not do enough to regulate its drivers.
But one driver with Uber in London said: "I don't think it is a fair decision. Uber offers a flexible schedule, and a weekly income."
http://www.bbc.com/news/uk-england-41358640