Tens of thousands of London private hire drivers could lose their licences due to new English reading and writing requirements, taxi app Uber said on Tuesday at the start of a court battle to halt the plans.San Francisco-based Uber, which allows users to book journeys at the touch of a button on their smartphone, has grown rapidly in recent years but faced bans and protests around the world as regulators play catch-up with technology disrupting traditional operators.Uber launched legal action in August after public body Transport for London (TfL) said that drivers should have to prove their ability to communicate in English, including to a standard of reading and writing which Uber says is too high. "It produces the profoundest of human effects. At one extreme it will lead to the loss of livelihood," Uber's lawyer Thomas de la Mare told the High Court in London.There are over 110,000 private hire drivers in the British capital, according to TfL but around 33,000 would fail to pass their renewal test due to the new language hurdle, de la Mare told the court, citing a calculation of data provided by TfL.The transport body has said it is important for public safety that drivers can communicate in English to an appropriate level and that it needs to better regulate the sector which has grown significantly in recent years, leading to congestion. It also wants drivers to have private hire insurance even when vehicles are not being used to carry passengers and for those like Uber to set up call centres open 24 hours a day.The proposals came partly as a response to demonstrations from drivers of London's famous black cabs, concerned that private hire firms are able to undermine their business model by not meeting the same standards and charging less for journeys. The High Court is due to hear the case until Thursday although it might be some weeks before a ruling.