SPANISH taxi drivers staged an anti-Uber strike yesterday over the ride-hailing app breaking a limit on the number of its cabs.

Normally packed taxi ranks at stations and airports were empty as licensed cabbies refused to pick up passengers, but their unions pledged free rides for the elderly, disabled and pregnant women.

Unions said US firm Uber and Madrid-based Cabify were flouting a law setting a maximum ration of one ride-hailing app cab for every 30 licensed taxis.

Taxis converged on Madrid early on Wednesday to take part in a midday protest from the city's main railway station to a square near Parliament.

Uber faced more woes at home on Tuesday when it emerged US federal prosecutors were probing industrial espionage claims by its former global intelligence manager Richard Jacobs.

The bombshell broke at a hearing in a civil action between Uber and self-driving car pioneer Waymo, founded by Google eight years ago.

Mr Jacobs testified that Uber had set up a unit called Marketplace Analytics to steal trade secrets from unnamed rivals overseas.

His attorney wrote a 37-page letter setting out the allegations, sent to Uber lawyers in May.

The allegations had been kept under wraps until the Justice Department passed them to US District Judge William Alsup last week — who recommended the department opened a criminal investigation.

The firm is already under attack around the globe for its unscrupulous hiring policies, precarious employment contracts, tax-dodging and leaks of drivers’ and passengers’ personal data.