Uber appealed before a British employment tribunal on Wednesday against a ruling that would give its drivers official worker status, as the company also battles against a threatened ban in London.
The landmark case brought by two Uber drivers could have far-reaching implications for people employed in Britain's "gig economy", many of whom complain about precarious working conditions and low pay. The US ride-hailing app may have to pay its drivers the national minimum wage of £7.50 (8.5 euros, $10) an hour if it loses the case.
Uber drivers are currently paid for each ride and are considered self-employed which means they are not entitled to benefits including paid holidays. A ruling in the case is not expected for weeks.
The Independent Workers of Great Britain (IWGB) trade union is representing the drivers, and staged a demonstration in central London.
Yaseen Aslam, one of the claimants, said drivers "face many struggles" and "carry all the risks". James Farrar, the other claimant, called Uber's business plan "brutally exploitative".
He called on London Mayor Sadiq Khan to make workers' rights a condition for renewing Uber's licence.
Transport authorities last week said they would not renew Uber's licence to operate in the capital, owing to concerns about public safety for passengers and the process of registration for drivers.
Uber, which has about 40,000 drivers and some 3.5 million customers in the British capital, has 21 days to lodge its appeal and can continue to operate until that process has concluded.
Adding to its headaches in London, Uber is also facing a sex discrimination case from a 44-year-old female driver also going to an employment tribunal.
She claims that the way in which the company asked her to operate is putting her and other women at risk.
"We believe that Uber's policies do not do enough to protect female drivers," said Nigel Mackay from the law firm Leigh Day, which is representing the driver.
He said that if a driver is faced "with threat of assault by a passenger and asks him to leave, she risks complaints and low ratings, with no right of reply, and ultimately may lose her job as a result".
An Uber spokesman said: "Drivers on the Uber app are free to log in and out as they want and can choose which trips they want to take, or cancel, without any penalty.
"If a driver doesn't want to go to a particular area there is no obligation for them to do so," he said.