Uber has lost its latest application for a licence to operate in London after Transport for London (TfL) found it “to be not fit and proper”.

TfL said that it did not have confidence that similar issues would not reoccur in the future, despite Uber having taken action on some areas

It marks the latest blow for the ride-hailing giant, which has been appealing for a licence renewal after initially losing its licence for London in 2017 and has been subsequently awarded two probationary licences, the last of which expired on Sunday.

TfL initially refused to renew the licence after revealing concerns over Uber London’s approaches to how medical certificates and DBS checks were obtained and to reporting serious criminal offences.

Although TfL said Uber has since made a number of positive changes and improvements, a pattern of failures have placed passenger safety and security at risk.

Breaches include unauthorised drivers exploiting vulnerabilities in the app, allowing them to upload their photos to other Uber driver accounts and pick up drivers as if they were the booked driver; at least 14,000 trips were booked in this way, leaving the journeys uninsured and passengers potentially at risk.

And a further failure meant that dismissed or suspended drivers were still able to create an Uber account and carry passengers, while other issues also meant that vehicles had been permitted for use without the correct insurance in place.

TfL added that it did not have confidence that similar issues would not reoccur in the future, despite Uber having taken action on some areas.

Uber now has 21 days to appeal, during which it can continue to operate pending any appeal and throughout any potential appeals process. However, it will remain open to TfL scrutiny, including over any changes to its app.

Helen Chapman, director of licensing, regulation and charging at TfL, said: “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.

“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.”

Responding in a tweet, Dara Khosrowshahi, Uber CEO, said: “We understand we’re held to a high bar, as we should be. 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.”

However, the decision has been welcomed by the Mayor of London, Sadiq Khan, who commented: “Keeping Londoners safe is my absolute number one priority, and TfL have identified a pattern of failure by Uber that has directly put passengers’ safety at risk.

“There is undoubtedly a place for innovative companies in London – in fact we are home to some of the best in the world. But it is essential that companies play by the rules to keep their customers safe.

“I know this decision may be unpopular with Uber users, but their safety is the paramount concern. 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.”

Trade union GMB also greeted the decision, building on its long-standing battle with the ride-hailing firm over drivers’ rights. Steve Garelick, GMB regional officer, said: “The company finally has to face up to the consequences of GMB’s landmark employment tribunal victory and change its ways.

“Uber pulled more stunts than a Hollywood movie, now it’s time for them to accept their responsibilities.

“We fully expect the Supreme Court to uphold the ruling of the Employment Tribunal, the Employment Appeal Tribunal and the Court of Appeal on drivers’ worker rights in July.”