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”.
Some 3.5 million passengers and 40,000 drivers use the Uber app in London.
TfL’s concerns include Uber’s approach to carrying out background checks on drivers and reporting serious criminal offences.
In a statement, Uber said: “Transport for London and the mayor have caved in to a small number of people who want to restrict consumer choice.”
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.”
He said Uber operated in more than 600 cities around the world, including more than 40 towns and cities in the UK.
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.”
Throughout its short, tempestuous life, Uber has clashed with regulators around the world – and more often than not it has come out on top.
Its tactic has often been to arrive in a city, break a few rules, and then apologise when it’s rapped over the knuckles. Some regulators have backed down, others have run the company out of town.
In London, despite protests from angry taxi drivers, the company has had a relatively easy ride until now.
But a wave of bad publicity about its corporate culture, its lax attitude to checks on its drivers and its treatment of this freelance army seems to have spurred TfL into action.
Make no mistake, Uber will use every legal avenue to fight this ban. It will argue that consumers, in the shape of the millions of mainly young Londoners who rely on its service, will be seriously let down if it can no longer operate.
But the courts will have to balance that with the serious concerns about public safety raised by TfL.