The chairman of a committee of MPs which has been studying working practices at Sports Direct has expressed "anger and disappointment" at the placing of a recording device during an unannounced visit to the firm's warehouse.
Members of the Business, Energy and Industrial Strategy Committee said they discovered the miniature camera during what was supposed to be a private discussion at the end of their tour of the warehouse at Shirebrook, Derbyshire, on Monday.
The firm's board has questioned the "veracity" of the device found by the MPs and insisted it had not authorised its use.
Committee chairman Iain Wright has written to Sports Direct boss Mike Ashley expressing anger and disappointment at the incident, saying it was "utterly unacceptable".
He wrote: "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.
"On behalf of the Select Committee 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.
"The covert recording and surveillance of a parliamentary committee without its knowledge or permission damages Sports Direct's reputation and it damages the ability of this committee to have faith or confidence in what we were told that day.
"lt would be reasonable for other interested parties, such as current and potential investors, audit teams and providers of finance to business, now to question whether they have been recorded without their permission during visits to Shirebrook.
"lt 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."
Mr Wright spoke on the phone to Mr Ashley, saying his suggestion that the device was planted by a committee member was a "spur of the moment misjudgment".
Mr Wright said that during the MPs' visit there were few opportunities to speak freely to agency staff, while access to some areas was delayed.
The MP reminded Mr Ashley that he told the committee earlier this year that an unannounced visit could go ahead at any time of day.