Thousands of London taxi drivers plan to sue Uber for damages alleging the ride-hailing firm operated unlawfully.
The planned group legal action could, if successful, hit Uber with a bill for millions of pounds.
The action, part of a planned anti-Uber campaign by black-cab drivers this year, claims it didn’t follow private hire rules between 2012 and 2018.
Uber said it “operates lawfully in London and these allegations are completely unfounded”.
The group action, which will be launched by law firm Mishcon de Reya, will allege that for six years Uber operated unlawfully in London.
Taxi rules in London mean that people have to contact a centralised office for minicabs, whereas they can hail a black cab on the street.
The lawsuit will claim that between 2012 and 2018, Uber let people hail its drivers directly, contravening those rules.
Litigation specialist RGL Management, which is also working with the cabbies to bring the case, said more than 4,000 had signed up so far.
There are about 5,200 further registrations being processed, with hundreds of enquiries per day, it said. The firm is funding a marketing campaign, and is looking to sign up as many as 30,000 eligible drivers.
A full-time driver over those six years could claim about £25,000 in lost earnings, it added. The group action is aiming to bring a case to the High Court no later than the first quarter of 2022.
An Uber spokeswoman said: “Uber operates lawfully in London and these allegations are completely unfounded.
“We are proud to serve this great global city and the 45,000 drivers in London who rely on the app for earnings opportunities, and are committed to helping people move safely.”
Uber has had a torrid history in the UK capital including previous lawsuits.
In February 2019 cab drivers lost a legal challenge which argued that Uber’s London operating licence was granted by a biased judge.
Uber then went on to lose its licence to operate in London in November 2019 after safety concerns.
But in September last year it was spared a London ban after a judge upheld an appeal against Transport for London’s decision over safety.