Couriers carrying emergency blood supplies and delivering passports have won improved employment rights in an important concession for workers in the gig economy.

The Doctors Laboratory, a company which provides pathology services to the NHS, has admitted that five cyclists, motorcyclists and van drivers carrying emergency blood supplies to hospitals and samples to laboratories, are not self-employed.

The company now concedes that the couriers, who are on a variety of different contracts, are workers, an official employment classification which entitles them to rights including holiday pay and a minimum wage. Self-employed contractors, who make the vast majority of drivers and riders in the courier and delivery industry, have no employment rights, beyond basic health and safety and anti-discrimination rules.

The firm, which is understand to employ more than 70 couriers, who are a mix of car drivers, motorcyclists and cyclists, would not confirm when or if it would be repaying holiday pay owed to the five workers.

“TDL is mindful of doing the right thing but as the case is ongoing we are unable to provide further comment at this time,” the company said.

TDL’s admission comes after a similar move by eCourier, a subsidiary of Royal Mail, which last month admitted it had wrongly classified one of its couriers as a self-employed contractor. It is now carrying out a review to work out how best to switch staff to worker status where it reflects their working arrangements. Both admissions came after legal action backed by the Independent Workers’ Union of Great Britain.

Other tribunals against taxi-hailing app Uber and courier firm CitySprint also both successfully argued drivers were officially “workers”.

Uber, which has 40,000 drivers in the UK, will appeal against the employment tribunal verdict in September. CitySprint has also launched an appeal after losing a similar case.

Jason Moyer-Lee, general secretary of IWGB, said: “Looking at how these cases have progressed in the past year and a half, there’s momentum for real change happening. Worker status in an inevitability in the gig economy. It is like dominoes falling.”

He said the IWGB would continue to pursue its case against TDL because the couriers argue they are employees – an even more secure classification than worker.

Employees have guaranteed additional benefits including sick pay and maternity leave as well as protection against unfair dismissal, statutory redundancy pay and the right to request flexible working.

Moyer-Lee said: “TDL’s recent admission of unlawful behaviour is further evidence that there has been widespread and rampant denial of employment rights with no consequence. But also that worker status is inevitable once these companies are challenged.

“In TDL’s case however worker status is not good enough, these couriers are employees. TDL would be wise to admit to the full extent of its behaviour and not try to weasel out of the situation on the cheap.”

The case will be heard between 13 and 16 November 2017.

• This article was amended on 4 July 2017. An earlier version said eCourier admitted to wrongly classifying hundreds of couriers as self-employed contractors. eCourier has admitted to wrongly classifying only one courier as a self-employed contractor. eCourier has said it’s carrying out a review into whether other couriers on similar contracts have been classified in the same way.