Transport bosses have been accused in the High Court of seeking to introduce new rules for private-hire vehicles that will lead to "indirect racial discrimination" and threaten the livelihood of tens of thousands of drivers.

The controversial Transport for London (TfL) package proposed for the capital includes a requirement that drivers undertake tests in reading and writing basic English.

Uber London Ltd, which has a private-hire vehicle (PHV) operator's licence, has launched a legal challenge with three individually licensed drivers - Hungarian national Sandor Balogh, Bulgarian national Nikolay Dimitrov and Imran Khan from Parkistan.

Tom de la Mare QC told a judge sitting in London that the "somewhat contrived" language requirement would over three years contribute to 70,000 applicants failing to obtain a licence and was "incapable of justification".

The QC said TfL's own modelling, first disclosed in January, revealed that the requirement and the changes to testing topographical and navigational skills should lead to a reduction in the number of PHV drivers to an estimated 61,000 by 2019-20 - about 45% of current levels.

The new rules, including having to provide new call centre facilities and meet unjustified insurance demands, were also likely to lead to additional costs for PHV operators running into millions of pounds, said Mr de la Mare.

TfL is arguing that the requirements are necessary for customer safety and public protection.

But Mr de la Mare said the TfL proposals would have a disproportionate impact on drivers from countries where English was not generally spoken and give rise to "indirect discrimination on grounds of race and nationality".

Many drivers, and those applying for licences, were economic migrants or asylum seekers given permission to remain in the UK who wanted to work and integrate into English life.

Mr de la Mare argued no real need had been shown for the English test and a drivers' ability to understand road signs and basic directional instructions was already sufficiently tested by the typographical test.

he said in all the time that PHV drivers had been operating, there was no evidence that restricted abilities to read and write English had led to problems.

Mr de la Mare said Mr Balogh and Mr Dimitrov had completed more than 2,000 trips as registered drivers "and never once in that time been requested to communicate (by reading and writing)".

The QC told Mr Justice Mitting: "If there is any such problem in relation to written communication, it is with respect small and cannot justify an impact of this magnitude."