The 20,000 part-time workers at Sports Direct, the retailer controlled by Newcastle United owner Mike Ashley, are employed on zero-hours contracts.
Zero-hours contracts mean that part-time staff at Sports Direct have no holiday or sick pay, and cannot be sure of how many hours they will work each week.
The part-time workforce at Sports Direct accounts for 90pc of its 23,000 employees.
The zero-hours contracts are in use despite the fact the company posted pre-tax profits of more than £200m in the last year and has introduced a generous bonus scheme for full-time staff.
Full-time workers at Sports Direct are set to collect a bonus worth more than £70,000 in company shares next month after the retailer hit profit targets.
The company has credited this bonus scheme, introduced in 2009, with revitalising the business and improving staff retention rates in the business.
However, most of Britain's other major retailers - including Tesco, Asda, Sainsbury's, Morrisons, and Marks & Spencer - do not use zero-hours contracts.
According to data from the Office for National Statistics, the number of workers in jobs without any guarantee of regular hours or pay nearly doubled during last year to reach 200,000.
The contracts now used by almost a quarter of Britain's major employers - legally allow firms to employ staff, often in low paid jobs, without any guarantee of actual work, or income.
The agreements have been heavily criticised, with Unison claiming they “present huge drawbacks in comparison to permanent regular work”.
Andy Sawford, the Labour MP for Corby, who is trying to ban the use of zero-hour contracts, told The Guardian : "It would be much better for Sports Direct to instead of offering bonus gimmicks, they should offer their staff the security of proper contracts.
"The zero-hours contracts are highly exploitative and suit the company because it keeps people in a fragile state where they are at the beck and call of their employers."