The chief executive of Hermes UK has admitted the company had not been as compassionate as it expected itself to be with its self-employed couriers, as a government minister called on HMRC to investigate the carrier’s zero-hours contracts.

An investigation by the Guardian in July accused Hermes of paying its self-employed couriers below the minimum wage, and suggested working conditions were stressful to the point that employees were too afraid to call in sick.

Speaking to in the wake of the story, Carole Woodhead said: “The key thing we took from that was that in some circumstances, we weren’t as compassionate as we expected ourselves to be. And in those cases we have apologised.”

Woodhead added that the investigation had triggered an internal review of the company’s practices, which had resulted in a new code of conduct, an internal panel for complaints from couriers and an external ombudsmen as a final recourse if people are still dissatisfied by their treatment.

Woodhead said: “We have committed to being absolutely bound by any decision they make about a case. Which I think is part of giving confidence externally that our standards are good, and that we treat people fairly.”

However, over the weekend news emerged that business minister Margot James has requested HMRC launch an investigation into Hermes’ use of the self-employed courier model and the claims it pays its couriers below the living wage.

Woodhead told that she thought Hermes could have been singled out because it’s a prominent company in the sector.

She said: “Self-employed courier drivers are common place across the industry, therefore it could be a bit of a lottery who’s name is going to come out.”

Frances O'Grady, general secretary at the TUC, is due to give a speech today at its national congress criticising zero hour contracts and the use of self-employed workers in the courier sector.