JJB shareholder Bill Gates is facing a £20m loss after the struggling sportswear retailer warned investors its shares could be worthless.

The Microsoft founder had shares in the up-for-sale retailer through a foundation he shares with his wife.

JJB Sports was put up for sale on Thursday and interested parties signed a non-disclosure agreement on Friday.

Private equity specialist Jon Moulton is believed to be interested in a bid through his Better Capital investment vehicle. However, sources claim he is not confident of striking a deal due to the number of parties involved.

French retail giant Decathalon and former JJB owner Dave Whelan are understood to have entered the race to buy the 180-store retailer, alongside turnaround firm OpCapita and the retailer’s largest shareholder, Invesco Asset Management.

Arch-rivals Sports Direct and JD Sports are also understood to be interested in acquiring some of JJB’s stores.

JJB lender Lloyds Banking Group said the bank is not interested in a debt-for-equity swap, while KPMG, which is running the sale process, said it has received “good interest” in the retailer.

Sports Direct is expected to report a bounce in sales, partly as a result of the pressure it has piled on JJB, when it reports its first-quarter results to the City this week.

Mike Ashley’s sportswear business is expected to meet its £270m “super-stretch” target for the current year, meaning the Newcastle United owner would pocket 8 million shares, worth £24m, if the company hits £340m in sales in 2015.