US ride-hailing app Uber on Wednesday lost an appeal in Britain against a ruling to grant workers' rights including the national minimum wage and holiday time to its drivers.
Uber, which says the drivers are self-employed, is not obliged to abide by the ruling until it has exhausted all possible appeals and can still appeal to the UK Supreme Court.
The case is seen as a landmark that could have major implications for thousands working in Britain's gig economy.
"Uber should accept the verdict and stop trying to find loopholes that deprive people of their hard-won rights and pay," said Tim Roache, general secretary of the GMB union.
Nigel Mackay from law firm Leigh Day, which was involved in the case, said: "We hope that Uber now faces its responsibilities instead of spending time and money in the courts attempting to deny its drivers these rights".
The case is being brought in the names of former Uber drivers Yaseen Aslam and James Farrar.
The company has about 40,000 drivers and 3.5 million customers in the British capital.
The US firm's lawyers had argued that the "agency model" -- with Uber acting as an agent between self-employed drivers and passengers -- has been used in the private hire industry "for many years".
The court decision was another setback for Uber on Wednesday after Transport for London said private hire vehicles like Uber and minicabs would have to pay the congestion charge for the city centre.
The charge, from which private hire vehicles were previously exempt, is a daily £11.50 (12.8 euros, $15) rate.