LONDON (Reuters) - A senior British lawmaker has demanded Sports Direct explain an alleged attempt to spy on a group of parliamentarians during a surprise visit this week to a company warehouse.

Several members of parliament (MPs) reported an attempt to hide a camera in a room where they were meeting in private on Monday, an incident described by MP Iain Wright in a letter to Sports Direct CEO Mike Ashley as "utterly unacceptable".

Wright also alleged in his letter that Ashley had suggested to him in a subsequent telephone conversation that the camera had been planted by a member of parliament's business committee, which has repeatedly clashed with the Sports Direct boss.

Committee members said at the end of their visit to the Shirebrook facility, which has been slated for poor working conditions, a woman brought them a tray of sandwiches, put it on a stool and tried to hide a camera underneath.

The incident was the latest in a series of public relations disasters for Sports Direct, a 450-store sportswear chain battling to improve its image after poor treatment of staff, including paying some less than the minimum wage, and corporate governance problems.

"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 misjudgment," committee chairman Wright wrote in the letter to Ashley, which was published on Wednesday.

A Sports Direct spokeswoman had no immediate comment on the letter, but on Tuesday the company's board said "it would like to make it clear that it did not authorize or have any knowledge of the possible recording device".

Sports Direct cut its profit forecast twice last month and has seen its share price slump this year. It said it was addressing shortcomings it admitted in its working practices.

(Reporting by Paul Sandle; Writing by Estelle Shirbon; Editing by Alexander Smith)