Allegations of exploitative working practices at one of the UK’s largest delivery firms are to be considered by an influential parliamentary committee after Hermes couriers claimed they had been told to accept pay cuts or lose their delivery rounds.

The allegation is one of a series referred to the business, energy and industrial strategy committee by the shadow secretary of state for employment rights, Andy McDonald, who spoke to several Hermes couriers and depot managers after the Guardian revealed many had felt compelled to do unpaid work during the pandemic.

McDonald said his office had heard claims the firm told some couriers their rates per delivery were to be cut – and that their livelihoods depended on them accepting because other couriers would simply be given their rounds if they refused.

He urged the committee’s chair, the Labour MP Darren Jones, to investigate further once MPs have had a chance to consider the evidence.

In a letter seen by the Guardian, McDonald said workers had claimed that, despite positive Covid cases, at least one depot “stayed open and wasn’t sanitised, just went on as if nothing had happened”. Moreover, he said he had gathered evidence of a “packet racket”, in which couriers said the customer pays for sending a large item, but the courier is only paid for delivering a small one.

The Guardian reported last month that some Hermes couriers, who are paid per delivery, said they felt compelled to help sort parcels for no pay so they could start their rounds on time. McDonald cited evidence from a depot manager who said this had been caused by Hermes refusing to provide the money to hire sufficient sorters at some of its subcontracted delivery units.

And he quoted another courier as saying they felt they had to work up to 14 hours some days, along with the inherent risk of catching Covid while they went door to door.

“It is an outrage that working people are receiving ‌no‌ ‌recompense‌ ‌for‌ ‌‌hours‌ ‌of‌ ‌their‌ ‌labour,‌ ‌or‌ ‌seeing‌ ‌enforced‌ ‌reductions‌ ‌to‌ ‌their‌ ‌pay‌ ‌with‌ ‌the‌ ‌threat‌ ‌of‌ ‌redundancy,” McDonald wrote.

“It is clear that bogus self-employment, inadequate employment protections and a lack of enforcement action are enabling these exploitative employment practices.

“With‌ ‌many‌ ‌drivers‌ ‌across‌ ‌the‌ ‌gig‌ ‌economy,‌ ‌along‌ ‌with‌ ‌other‌ ‌key‌ ‌workers,‌ ‌having‌ ‌spent‌ ‌the‌ ‌past‌ ‌year‌ ‌putting‌ ‌their‌ ‌lives‌ ‌on‌ ‌the‌ ‌line‌ ‌to‌ ‌keep‌ ‌our‌ ‌country‌ ‌going‌ ‌through‌ ‌the‌ ‌Covid‌ ‌pandemic,‌ ‌whilst‌ ‌the‌ ‌companies‌ ‌that‌ ‌they‌ ‌work‌ ‌for‌ ‌have‌ ‌raked‌ ‌in‌ ‌vast‌ ‌profits,‌ ‌it‌ ‌is‌ ‌only‌ ‌right‌ ‌that‌‌ we‌ ‌ensure‌ ‌that‌ ‌we‌ ‌do‌ ‌all‌ ‌that‌ ‌we‌ ‌can‌ ‌to‌ ‌put‌ ‌an‌ ‌end‌ ‌to‌ ‌such‌ ‌unfair‌ ‌and‌ ‌pernicious‌ ‌practices.”‌

Many of the sources were referred to McDonald’s office by the Guardian after they contacted the paper following the original report in April.

Hermes said: “We are disappointed McDonald did not come to us with his concerns and allow us to fully investigate and address these allegations,” adding that they had come from a small number of its workers.

A spokeswoman added: “HMRC recently concluded that courier earnings are above minimum wage and that our model is genuine self-employment.” And she said Hermes workers were able to benefit from representation by the GMB union.

She did not explicitly deny the allegation that some couriers had been told they would lose their rounds unless they accepted rate cuts. But she said: “We are continuously reviewing some courier rates to ensure that they are in line with local markets and our fair pay commitments” and that, on average, couriers had received a rate increase in recent years.

Hermes denied that any depot had stayed open despite a Covid case, saying: “Throughout this pandemic, we followed strict protocols at all sites.” Responding to claims of a “packet racket”, she said: “This is not correct.” She acknowledged that items were sometimes incorrectly banded, but that Hermes often corrected this and couriers were able to do so as well.

Hermes said it had “taken strong action to address the small number of cases where couriers were allegedly not being paid” and insisted that it did not believe underfunding of depots on its part was a factor.

The firm did not deny that some couriers had worked long hours during the pandemic, but said they had done so voluntarily and had been given reasonable protections against Covid.