The "self-employed plus" arrangement will give couriers working for Hermes individually negotiated pay rates allowing them to earn at least £8.55 per hour, plus holiday pay for up to 28 days a year on a pro rata basis.
The model is opt-in, meaning that couriers wanting to continue working on their current self-employed basis will see no change to their arrangements. Couriers choosing to join the scheme will also be able to join the GMB and gain full union representation.
The agreement follows a victory for the GMB against Hermes in the Leeds employment tribunal last year, when a group of 65 couriers were found to be 'workers' entitled to basic rights, instead of self-employed contractors.
Employment law expert Stuart Neilson of Pinsent Masons, the law firm behind Out-Law.com, said the agreement was notable as trade unions normally negotiated collective agreements on behalf of groups of employees, rather than workers.
"The reality of it is that this is something which Hermes has been forced into doing by virtue of the fact that it lost the employment tribunal case," Neilson said.
"Employers are only going to do this if they think they have no choice. It’s a recognition of the fact that trade unions have been mounting a reasonably successful campaign to get rights for these workers," Neilson said.
GMB general secretary Tim Roache said Hermes was "showing that the gig economy doesn’t have to be an exploitative economy" and added that other employers should take note of the arrangement.
The so-called 'gig economy' has been under increasing scrutiny in the last few years with a number of high-profile cases seeking to clarify the status of workers. In December, the Court of Appeal ruled that a group of Uber drivers were ‘workers’, entitled to a minimum wage and paid holidays.
However not all cases have gone the way of the workers. Last year the Independent Workers' Union of Great Britain lost a fight for judicial review of a 2017 decision saying cyclists delivering food on behalf of Deliveroo were self-employed and not entitled to unionise. The High Court ruled that the riders had the flexibility to turn down work or find a substitute, meaning they could not be classified as workers.
In 2017 an independent report produced by Royal Society of Arts chief executive Matthew Taylor recommended a number of reforms to protect workers' rights. Last December the government introduced new legislation implementing the majority of Taylor's recommendations, although it has commissioned research to help clarify workers' status.
The gig economy has also been under scrutiny by the tax authorities with HM Revenue & Customs increasing its efforts to recoup payroll tax from businesses wrongfully categorising workers as self-employed.