The board of Sports Direct has denied any knowledge of an attempt to bug MPs who were on a surprise visit at the firm's warehouse.

The sportswear giant was responding following an extraordinary incident that is alleged to have occurred when six MPs from the Business and Skills Committee visited its controversial Shirebrook warehouse in Derbyshire.

The MPs claim an attempt was made to smuggle in a recording device behind a plate of sandwiches to record their discussions in a room at the site at the end of the visit.

Sports Direct said: "The board is disappointed that reporting of a possible recording device (the veracity of which has yet to be determined) has overshadowed the truly important issues that this visit should have focused on – the true working conditions and worker satisfaction at Shirebrook."

It added: "The board would like to make it clear that it did not authorise or have any knowledge of the possible recording device."

Sports Direct has been under fire from unions, investors and politicians over claims of Victorian workhouse conditions at the warehouse, and over its corporate structure.

Among issued raised were that staff being kept on site at Shirebrook for long periods after their shifts for body searches, putting them below the legal minimum wage.

The MPs organised an impromptu check to see whether Sports Direct had improved employment methods.

Political football

They only gave notice on Monday morning (8 November) that they would visit the Derbyshire site.

After a three-hour tour, the MPs gathered in a private room, and were served sandwiches. However, Anna Turley, MP for Redcar, said the lady who had served the sandwiches also left a recording device in the room. Turley said: "I went over to pick up the device and there it was: a camera and a recording device for the conversation that we were having privately. I'm very disappointed."

Sports Direct has promised a number of changes since Mike Ashley, the company's billionaire majority owner, appeared before the committee in June.

Ashley said: "I stand firmly behind the people of Sports Direct, who through no fault of their own have been made a political football by MPs and unions."