London's transport authority said Friday that it will not renew Uber's license, saying the company is not "fit and proper."

Transport for London cited the company's approach to reporting serious criminal offenses, and its use of software that prevented regulators and law enforcement from monitoring the app.

The agency made the announcement from its Twitter account.

London mayor Sadiq Khan said he "fully supports" the decision to not renew the license when it expires September 30.

"All companies in London must play by the rules and adhere to the high standards we expect -- particularly when it comes to the safety of customers," he said in a statement. "Providing an innovative service must not be at the expense of customer safety and security."

Uber has 21 days to appeal the decision and can continue to operate during that period. Its representatives were not immediately available for comment.

The app works with over 40,000 drivers in the city and has been used by 3.5 million Londoners.

Uber has sparked numerous controversies in major cities around the world over passenger safety, background checks and driver pay.