The GMB union is taking legal action against Hermes as part of its wider campaign against the gig economy.

The case is being brought on behalf of eight Hermes couriers who claim they are being denied their workers’ rights. Proceedings have been lodged with the Employment Tribunal by solicitors Leigh Day.

If the case is successful the claimants and other Hermes couriers currently classed as self-employed could be reclassified as employees, potentially giving them full employment rights including holiday pay, the national living wage and pension rights.

Last autumn, HMRC said it was "considering" information supplied to it by Frank Field MP in regards to employment practices at the operator.

Earlier this month the Work and Pensions Committee, which Field was chairman of until it was dissolved ahead of next month's general election, criticised self-employment contracts used by Hermes and other gig economy companies, as “gibberish” and “almost unintelligible”.

Maria Ludkin, GMB legal director, said: “GMB will fight bogus self-employment and exploitative practices whenever and wherever we can.

“Under the false claims of ‘flexibility’, Hermes seems to think it’s acceptable to wriggle out of treating its workers with respect.

“Guaranteed hours, sick pay, pension contributions – these aren’t privileges to be bestowed when companies feel like it, they are the legal right of all UK workers."

Michael Newman, of Leigh Day, said: “We believe that Hermes are deliberately avoiding giving their couriers the rights to which they are entitled.

“They do so by labelling the couriers who work for them as self-employed, when the reality is different. We have started employment tribunal proceedings in order to challenge this, so that these couriers can enforce their rights as workers.”

Hermes declined to comment.

Hermes is the third delivery firm GMB has targeted. The union is also pursuing a legal case against DX Group and UK Express.

The GMB was successful in a case against Uber last year when the London Employment Tribunal found in favour of the union. Uber is currently contesting the decision in the employment appeal tribunal.