LONDON (Reuters) - Riders at food courier firm Deliveroo will begin the process of seeking employment rights such as the minimum wage at a tribunal on Thursday, in a further challenge to the flourishing “gig economy.”

A deliveroo worker cycles along a pedestrianised road in Liverpool, Britain, October 18, 2017. Picture taken October 18, 2017. REUTERS/Phil Noble

The company’s roughly 15,000 drivers have become a familiar sight in Britain since 2013, tapping into the rapidly growing demand for takeaway food from restaurants.

They operate in the gig economy, where many people work for different firms without a fixed contract, and are self-employed, entitling them to only basic rights.

The firm says the vast majority of its couriers enjoy flexible working but some unions and MPs have criticised its practices and say riders should be entitled to rights such as holiday entitlement and the minimum wage.

Law firm Leigh Day, which is bringing the action, said it had submitted claims on behalf of 45 couriers and that a preliminary hearing will be held at an employment tribunal on Nov. 2, where a timetable for the case will be set.

“Our argument is that these riders are controlled, managed and disciplined by Deliveroo and that they clearly do not carry out their own delivery businesses, as Deliveroo argues,” said lawyer Annie Powell.

“We are claiming that these riders are employees of Deliveroo and that Deliveroo is acting unlawfully in denying riders these rights.”

Deliveroo said most of its riders wanted to remain self-employed and that they earned on average more than the minimum wage.

A spokesman said the company was also calling for a change in legislation to provide other entitlements to its couriers.

“We want to be able to offer riders greater security such as injury pay and sick pay alongside flexible work, but we are currently constrained by the law,” the spokesman said.

“That’s why we have called on the government to update legislation so we can end the trade-off between flexibility and security that currently exists in law.”

Leigh Day won a case last year on behalf of two Uber [UBER.UL] drivers entitling them to workers’ rights such as the minimum wage which the Silicon Valley firm has since appealed.