Unite, the union, has accused Sports Direct of breaking promises to offer store staff guaranteed hours rather than zero-hours contracts.
At its shareholders' meeting last year, the retailer said it would offer staff who requested it a certain number of hours a week.
But 12 months later Unite said Sports Direct was still advertising for staff without a minimum number of hours.
Sports Direct has been approached for a comment.
Unite said the job adverts prove that the retailer is still using zero-hours contracts and not offering guaranteed hours, clearly stating: "This role has no guaranteed hours of work, hours of work can therefore vary from week to week and, as a result, there may be weeks when no hours of work are offered."
Sports Direct holds its annual shareholders' meeting at its Shirebrook headquarters in Derbyshire on Wednesday.
Last month the controversial retailer said that revealed profits more than halved to £113.7m, partly because the weaker pound made its imported clothing more expensive.
On the agenda is the re-appointment of chairman Keith Hellawell.
A string of investment groups plan to vote against his re-election after expressing concern that not enough progress has been made on corporate governance and labour relations.
Unite assistant general secretary Steve Turner said: "This revelation shows it is 'business as usual' at Sports Direct and casts doubt on just how sincere it is about cleaning up its act."
In recent months, Sports Direct has bought 26% stake in Game Digital, increased its stake in Debenhams, acquired lingerie firm Agent Provocateur and snapped up the US sports clothing and outdoor equipment chains Bob's Stores and Eastern Mountain Sports.