Uber has launched an appeal against a landmark employment tribunal ruling that its minicab drivers should be classed as workers with access to the minimum wage, sick pay and paid holidays.

The taxi-app company filed papers with the appeal tribunal on Tuesday in an attempt to overturn the October judgment that, if it stands, could affect tens of thousands of workers in the gig economy.

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The move came as several dozen Uber drivers picketed City Hall on Wednesday holding placards demanding Transport for London, which licences Uber as a private hire operator in the capital, “end sweated labour now”. It also mounted a protest at the City of London offices of Salesforce, a US computing company that is a major Uber client.

Two Uber drivers, James Farrar and Yaseen Aslam, took Uber to court on behalf of a group 19 others who argued that they were employed by the San Francisco-based company, rather than working for themselves. Uber’s business model has been based on treating drivers who log on to its app as self-employed contractors and taking a cut of their fares, which Uber dictates.

The employment tribunal judges were scathing about Uber’s case that drivers who use its phone app to pick up fares were self-employed.

“The notion that Uber in London is a mosaic of 30,000 small businesses linked by a common ‘platform’ is to our minds faintly ridiculous,” they said. “Drivers do not and cannot negotiate with passengers … They are offered and accept trips strictly on Uber’s terms.”

Farrar said Uber’s appeal was expected but was “really disappointing”. “It means we have to fight again, but why?” he said. “It is just because they don’t want to pay the minimum wage. We are confident. Our case is rock solid and the original judgment was emphatic.”

Jo Bertram, Uber’s UK general manager, said: “Tens of thousands of people in London drive with Uber precisely because they want to be self-employed and their own boss. The overwhelming majority of drivers who use the Uber app want to keep the freedom and flexibility of being able to drive when and where they want.”

Meanwhile, 25 more Uber drivers are planning to claim workers’ rights from Uber and have joined the legal action the law firm Leigh Day is bringing with the GMB union.

“Since the judgment was issued, we and GMB have spoken to hundreds of Uber drivers who wish to claim compensation for Uber’s failure to provide these entitlements in the past, as well as to ensure that they are paid at least the national minimum wage and holiday pay in future,” said Nigel MacKay, the lawyer representing the claimants.

“We are issuing claims on behalf of those drivers and the latest 25 claimants who have joined the legal action will be included in claims for compensation. We anticipate issuing further claims on behalf of drivers in the coming weeks.”

Leigh Day believes there may be thousands of drivers who can claim for the money and benefits they have not received as drivers for Uber.

Uber’s appeal comes amid mounting concern within the government about the growing trend towards self-employed workforces. The government has recently announced a six-month review of modern working practices and HMRC is setting up a new unit, the employment status and intermediaries team, to investigate companies.

Last week Frank Field, the chairman of the House of Commons work and pensions select committee, published a report including the testimonies of 83 Uber drivers, which claimed that they had almost no independence.

Field’s report, contested by Uber, said the company dictates drivers’ working patterns once they have logged on, imposes lockouts from its system if drivers turn down too many jobs, and has raised its commission while cutting the rates drivers can charge. This, combined with the cost of the vehicles needed to meet Uber’s requirements, is creating “chronically low pay” and insecurity, the report said.