Tax inspectors have been asked to consider whether delivery firm Hermes should be investigated over allegations some of its couriers receive less than the minimum wage.
Business minister Margot James has written to HM Revenue and Customs over claims by some delivery staff that they are entitled to the minimum amount but do not receive it, the Department for Business, Energy and Industrial Strategy confirmed.
The firm's couriers are classified as self-employed and The Guardian on Monday reported that HMRC will be asked to examine whether that is correct.
It follows claims made in July that some couriers feel they are "treated like dirt" and have faced losing work for attending hospital appointments or tending to sick relatives.
The details of complaints made about Hermes by current and former staff were revealed in a letter sent to PM Theresa May by the chairman of the Commons Work and Pensions Select Committee, Frank Field, urging her to launch an investigation.
Hermes said at the time it would look into the allegations made by Mr Field but insisted it had an "extremely committed and loyal network of couriers who enjoy their work and deliver high standards of service in return for for good rates of pay".
Mr Field told The Guardian some staff members "seem to be enforcing an employee contract under the cover of self-employment".
Hermes told the newspaper it was confident its agreements with couriers represented "legitimate self-employment" but would co-operate with any new probe.