Thousands of Sports Direct warehouse workers are expected to receive back pay totalling about £1m, according to Unite the union.

The payments, backdated to May 2012, cover unpaid searches at the end of shifts at Sports Direct’s Shirebrook warehouse and could be worth up to £1,000 for some workers, Unite estimates.

Sports Direct founder Mike Ashley admitted to MPs in June that staff at its Shirebrook warehouse were effectively paid below the minimum wage, owing to rigorous searches after shifts. 

The admission came as part of a probe by Parliament’s Business, Innovation and Skills Committee into Sports Direct’s controversial employment practices, following media revelations.

Shirebrook staff directly employed by Sports Direct and through employment agency The Best Connection are expected to start receiving pay at the end of this month, Unite said.

Unite assistant general secretary Steve Turner branded it a “significant victory” in the union’s campaign to “secure justice and dignity” for Sports Direct staff.

However, Unite said it understands that as many 1,700 Transline agency workers at Shirebrook may only initially receive half the back pay they are owed. Unite claims the agency is refusing to honour its commitments from when it took over from Blue Arrow at the warehouse two years ago.

However, a Transline spokesman said: “We are making all payments required in full compliance with HMRC.” 

Sports Direct has yet to respond to a request for comment.

Reports this weekend suggested that Sports Direct chairman Keith Hellawell and other directors are facing a mutiny from some of its largest shareholders at next month’s annual meeting.

Almost one in four of the retailer’s staff quit last year, including store managers and senior bosses, according to its annual report.