Uber drivers are estimated to be more than £18,000 out of pocket because the ride hailing company refuses to recognise a two-year-old ruling entitling them to holiday pay, a minimum wage and rest breaks.

The law firm Leigh Day – acting for the GMB union, which brought the action against the tech giant – calculates that its 40,000 drivers are all owed almost £11,000 in wages and more than £8,000 in holiday pay. But Uber is continuing to appeal the ruling, made two years ago at the central London employment tribunal.

“These figures lay bare the human cost of Uber continuing to refuse to accept the ruling,” said GMB legal director Sue Harris. “While the company is wasting money losing appeal after appeal, drivers are up to £18,000 out of pocket. That’s thousands of drivers struggling to pay their rent, or feed their families. It’s time Uber admits defeat and pays up. The company needs to stop wasting money dragging its lost cause through the courts. Instead, Uber should do the decent thing and give drivers the rights to which those courts have said they are legally entitled.”

However, a spokeswoman for Uber said “almost all” taxi and private hire drivers had “been self-employed for decades”, long before Uber existed. She quoted an Oxford University study based on a poll commissioned by Uber, which found that its drivers make more than the London Living Wage. She added: “If drivers were classed as workers, they would inevitably lose some of the freedom and flexibility that come with being their own boss.”

Since the ruling, Uber says it has given drivers more control over how they use its app, plus sickness, maternity and paternity protection.

“We think the Employment Appeal Tribunal fundamentally misunderstood how we operate,” the spokeswoman said. “For example, they relied on the assertion that drivers are required to take 80% of trips sent to them when logged into the app, which has never been the case here.”

In its recent accounts, Uber London acknowledges that the self-employed status of its drivers is disputed. It says: “The Uber Group [is exposed] to numerous legal and regulatory risks, including the application, interpretation and enforcement of existing regulations … as well as risks related to … the company’s classification of drivers as independent contractors.”