LONDON (Reuters) – London’s transport bosses said on Monday that all drivers of private hire vehicles must speak, listen to, read and write English to a set level, intensifying a battle with taxi app Uber [UBER.UL] which says the expected standard is too high.

Earlier this year, the capital’s transport authority said it would introduce the measure as part of a series of stricter rules on apps such as Uber and private hire firms like Addison Lee whilst supporting the city’s iconic black cabs.

The move prompted San Francisco-based Uber, which allows users to book journeys on their smartphone, to take legal action arguing that the written component was too demanding.

But on Monday, regulator Transport for London (TfL) said drivers will have to take either an English proficiency test or provide proof, such as a British school qualification, that they can meet the required level.

“Drivers must be able to communicate with passengers to discuss a route, or fare, as well as reading and understanding important regulatory, safety and travel information,” TfL said in a statement.

A hearing in the case brought by Uber, whose investors include Goldman Sachs and Alphabet Inc unit GV, formerly known as Google Ventures, is due in December.

(Reporting by Costas Pitas; editing by Stephen Addison)