Uber's application for a new licence to operate in London has been rejected on the basis that the company is not a "fit and proper" operator.
An Uber spokesman said the company was taking steps to improve security for its drivers and that they are paid more than the minimum wage, enjoying the flexibility offered by the app.
The ride -sharing app has faced numerous regulatory obstacles in markets around the world, but having its licence abolished in London would be one of the biggest blows it has faced during its short history.
Transport for London (TfL) said Uber had not met "rigorous regulations" created to ensure passenger safety.
When TfL proposed new private hire rules that would have limited Uber's operations in 2015, more than 200,000 people signed a petition to oppose them.
The startup works with over 40,000 drivers in the city and has been used by 3.5 million Londoners. The group of MPs labelled Uber an "unfit and improper operator" because of its failure to do enough to protect the safety of its passengers in London. That decision was quickly overturned by an Italian court, however, after Uber appealed the decision. Transport for London said the company could continue to operate until any appeals process was exhausted.
'Providing an innovative service must not be at the expense of customer safety and security'.