The long-running argument over the status of drivers at ride-hailing firm Uber will go before the Court of Appeal on Tuesday.
Uber drivers will be joined by hundreds of workers from other gig economy companies in a march through London ahead of the case.
The Independent Workers Union of Great Britain (IWGB), which is involved in the case, said it is expected to be the biggest “precarious workers” march ever held in the UK.
Couriers, riders, outsourced cleaners, restaurant workers and others will be involved while a rally will also be held in Glasgow.
The protesters will march to the Royal Courts of Justice, then go to the University of London, where outsourced workers, including cleaners, receptionists and security officers, will be on strike to end outsourcing, before passing NHS contractor The Doctors Laboratory, where medical couriers say their pay has been cut.
Uber case co-claimant and IWGB United private hire drivers branch chairman James Farrar said: “What is clear from the different kinds of workers supporting us in this demonstration is that unity among precarious workers has never been stronger and together we will defeat the dishonest bosses that are trying to do away with our most basic employment rights.”
The GMB, which is also involved in the case, said Uber drivers are estimated to be an average of £18,000 out of pocket two years after the company lost an employment tribunal case over the employment status of drivers.
Uber took the case to the Employment Appeals Tribunal last year and lost.
Sue Harris, the GMB’s legal director, said: “These figures lay bare the human cost of Uber continuing to refuse to accept the ruling of the courts.
“While the company are wasting money losing appeal after appeal, their drivers are up to £18,000 out of pocket for the last two years alone.”
An Uber spokesman said: “Almost all taxi and private hire drivers have been self-employed for decades, long before our app existed.
“A recent Oxford University study found that drivers make more than the London living wage and want to keep the freedom to choose if, when and where they drive.
“If drivers were classed as workers they would inevitably lose some of the freedom and flexibility that comes with being their own boss.
“We believe the Employment Appeal Tribunal last year fundamentally misunderstood how we operate. 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 in the UK.
“Over the last two years we’ve made many changes to give drivers even more control over how they use the app, alongside more security through sickness, maternity and paternity protections. We’ll keep listening to drivers and introduce further improvements.”