Uber Technologies Inc.’s licence to operate in London won’t be renewed, Transport for London announced Monday. TfL regulates taxis and private-hire services in London; it said safety concerns still surround Uber even though the company has made efforts to improve operations.

Uber has 21 days to appeal the decision, and it can continue to operate during that time. In addition, the BBC reported a decision on an appeal from a magistrates' court could take weeks or months and the company could keep operating during that time.

“While we recognise Uber has made improvements, it is unacceptable that Uber has allowed passengers to get into minicabs with drivers who are potentially unlicensed and uninsured,” said Helen Chapman, director of licensing, regulation and charging at TfL. “It is clearly concerning that these issues arose, but it is also concerning that we cannot be confident that similar issues won't happen again in future.”

If Uber appeals, it will be able to argue its case to a magistrate that it has put in place sufficient safety measures, Chapman said.

Uber CEO Dara Khosrowshahi said in a tweet that TfL’s decision was wrong.

“We understand we’re held to a high bar, as we should be,” Khosrowshahi tweeted. “But this TfL decision is just wrong. Over the last two years we have fundamentally changed how we operate in London. We have come very far — and we will keep going, for the millions of drivers and riders who rely on us.”

The San Francisco-based human cloud, ride-sharing firm had been operating on a 15-month probationary licence that was extended by two months in late September. It received the probationary licence in June 2018 after TfL initially decided against issuing a new licence.

In its decision on Monday, TfL said several safety breaches prompted it to decline the renewal of Uber’s private operator’s licence. One issue: Uber’s systems allowed unauthorised drivers to upload their photos to other drivers’ Uber accounts.

“This allowed them to pick up passengers as though they were the booked driver, which occurred in at least 14,000 trips — putting passenger safety and security at risk,” according to TfL. “This means all the journeys were uninsured and some passenger journeys took place with unlicensed drivers, one of which had previously had their licence revoked by TfL.”

Another problem cited by TfL: Dismissed or suspended drivers were still able to create Uber accounts and carry passengers.

“TfL recognises the steps that Uber has put in place to prevent this type of activity,” the agency wrote. “However, it is a concern that Uber’s systems seem to have been comparatively easily manipulated.”

Other breaches have occurred, including several insurance-related issues, TfL said.

London Mayor Sadiq Khan supported TfL’s decision.

“I know this decision may be unpopular with Uber users but their safety is the paramount concern,” Khan tweeted. “Regulations are there to keep Londoners safe, and fully complying with TfL’s strict standards is essential if private hire operators want a licence to operate in London.”

However, the Confederation of British Industry said dialogue between the company and TfL should continue.

“Uber’s popularity shows that customers value the service and choice that their innovative technologies offer,” CBI Chief UK Policy Director Matthew Fell said in a statement.

“TfL of course has to be confident around safety issues, so we’d encourage both sides to continue the dialogue to determine what changes are required in order that Uber’s customers can continue to enjoy the service in the long term,” Fell said.