The chairman of the business select committee has asked Mike Ashley to explain the use of a camera in an apparent attempt to secretly record MPs’ conversations when they visited Sports Direct’s warehouse.

Iain Wright, in a letter to the company’s founder and chief executive, said the action was consistent with the controlling way the MPs were dealt with during Monday’s visit. The Labour MP said Ashley had suggested the camera was placed under a tray of sandwiches by a committee member in the meeting room at the Shirebrook site in Derbyshire.

Wright and five other members of the committee visited the warehouse at short notice and asked to be shown round after Ashley invited them to do so in June. Ashley made his open invitation when the committee questioned him over working practices at Sports Direct, which he promised to improve.

After a tour, which one member described as a wild goose chase, the MPs were shown to a meeting room to discuss the day. They said a member of staff placed a plate of sandwiches on a stool and put the camera, which was used to record conversations earlier during the visit, by the plate.

In his letter, Wright said: “For an organisation in the process of reviewing its corporate governance and working practices, it is difficult to understand how a representative of the company thought that such an action would assist Sports Direct and why this action was authorised.

“I am asking you for an explanation of how and why the camera came to be placed in the room, who authorised its placing and what steps you have taken as a result … It is staggering to think that nobody thought to think of the long-term damage such an act, amateurishly carried out, could inflict upon your company.”

Sports Direct published a statement on Tuesday saying it did not know about or authorise the use of a camera and questioning “the veracity” of the story.

The board complained that the MPs arrived on a day when Ashley was not at the warehouse and that the camera incident had overshadowed positive comments made by staff about the company. Ashley added that Sports Direct was being used as a political football.

Wright said Sports Direct’s statement was “wholly unsatisfactory”, adding: “I will assume your initial suggestion to me during our telephone conversation that the device was planted by a committee member was a spur of the moment misjudgement rather than what would be a very serious allegation.”

He said he would have liked Ashley to have been at the site but that diary clashes did not allow this. Karen Byers, global operations head and one of Ashley’s closest associates, was understood to have shown the MPs round in Ashley’s absence.

Wright said the MPs were treated with courtesy on their visit but had little chance to speak to employees without being monitored and faced delays in being allowed into certain parts of the site. Staff interventions were “obviously organised and stage managed”.

Wright said the incident had undermined the committee’s faith in Ashley’s promises to improve conditions at Sports Direct after the MPs accused him of running the company like a Victorian workhouse. He said investors, auditors and other visitors to Shirebrook might justifiably question whether they had been secretly recorded.

Wright concluded: “I remain prepared to offer support to your efforts to reform your business in a way that treats all workers fairly and with respect … However, you do need to demonstrate a degree of trust, openness and constructive engagement that I hoped to establish but was so unfortunately lacking on our visit to Shirebrook.”