Transport for London said the decision was based on the way drivers' background checks were completed, how criminal offences were reported and the use of software created to stop regulators accessing its app.
London police complained this year that the app, which is backed by Goldman Sachs and BlackRock, was either not disclosing, or taking too long to report, serious crimes including sexual assaults and that this put the public at risk.
TfL said on Friday that Uber was "not fit and proper" to hold a licence because it had demonstrated "a lack of corporate responsibility in relation to a number of issues which have potential public safety and security implications". Tom Elvidge, Uber's London general manager, pointed out that over 3.5 million citizens of London use the app regularly, and 40,000 licensed drivers therein are making a living as Uber drivers, now to be shut down unless something changes. The company has 21 days to appeal the decision, and is allowed to continue working and driving throughout the process.
This added fuel to the suggestions that attacks on Uber had been trumped up following pressure on London mayor Sadiq Khan by lobbyists.
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This is especially embarrassing for a firm that prides itself on helping other companies thwart online cybersecurity attacks. But it "resulted in access to nonpublic information" that "may have provided the basis for illicit gain through trading".
Uber, which has 40,000 drivers in the capital and millions of users, took to Twitter to promote its Change.org petition to reverse the ban, which has garnered 737,000 signatures at the time of writing, and defended its business in a series of tweets. Three unnamed members of the Greater London Authority were also present, according to TfL documents. "Obviously I am pleased that he has acknowledged the issues that Uber faces in London", Khan said.
Uber could remain on London's streets for more than a year - despite being banned by the capital's transport body last week.
The comments mark a more conciliatory tone from the mayor who had criticized the firm's petition to "Save Uber" after news of Uber's removal broke Friday.
While many would cite the previous monopoly of taxi companies, and their rude, expensive, largely uncharted services, and think, "well, good", the impact on drivers goes far beyond the on-road competition for fares.
They also claim the Uber software blocks "officials from undertaking regulator or law enforcement duties".
"If you play by the rules you're welcome in London, if you don't, don't be surprised if TfL takes action against you".