The San Francisco-based company, which offers an app that allows people to book journeys on their smartphones, lost a March court battle against Transport for London (TfL) -- one of a number of setbacks as authorities crack down on the business -- but was granted an appeal on Tuesday

Uber has cited TfL data showing that the language criteria, which would involve written tests for many, could mean about 33,000 private-hire drivers out of a total of around 110,000 operating in London would be unable to renew their licenses.

Drivers applying for a new or renewed license had until the end of September to prove they meet the more rigorous English language criteria, pushed by London Mayor Sadiq Khan partly in response to pressure from drivers of the city's traditional black cabs, who fear their business model is being undercut.

But on Tuesday TfL said the plans would not come into place until April next year, after a Court of Appeal hearing due in February.

"We maintain that all licensed drivers must be able to communicate in English at an appropriate level," a TfL spokesman said. "We will continue to robustly defend this position at the appeal."

Uber welcomed the decision to allow its appeal, which comes after a series of setbacks in Britain and around the world.

"We're pleased to have secured this appeal to defend tens of thousands of drivers who risk losing their livelihoods because they can't pass an essay writing test," Uber's London General Manager Tom Elvidge said on Tuesday.

Uber has endured a tumultuous few months after a string of scandals involving allegations of sexism and bullying at the company, leading to investor pressure which forced out CEO and co-founder Travis Kalanick.