Uber has lost its license to operate in London, dealing a massive blow to the hugely-popular-yet-beleaguered taxi-hailing app company.

The company's current license to operate in the British capital expires on September 30. Its drivers can continue to operate until that date, but Uber has just 21 days to appeal the ruling.

Transport for London (TfL) said the company was not a “fit and proper” operator in its ruling, stating that “Uber’s approach and conduct demonstrate a lack of corporate responsibility”, particularly with regard to policing its drivers.

Thousands of drivers in limbo

Uber has more than 40,000 drivers on its books in London, with 3.5 million Londoners using the app to hire cars. 

While it's been praised for its ease of use, GPS-based pick-ups and affordable fares, Uber has regularly faced criticism from London's traditional black cab services, who argue that Uber's financial practices and lack of regulation amount to unfair competition. 

TfL also found fault with Uber's “approach to explaining the use of Greyball in London – software that could be used to block regulatory bodies from gaining full access to the app and prevent officials from undertaking regulatory or law enforcement duties”.

Uber has frequently courted controversy around the globe prior to today's ruling. Globally, Uber's driver hiring practices negate some of the license requirements that other operators have to deal with, while there have been numerous allegations of rape and assault against its drivers.

At a board level, Uber's former CEO Travis Kalanick was ousted following claims that he fostered a negative workplace culture where sexual harassment was commonplace.

Today's ruling, in one of the world's leading capital cities, will set a troubling precedent for Uber, with other cities and countries in which it faces opposition now likely buoyed to take firmer action against the company.

This is a breaking story. We will update as new details emerge.