The Government says Smith's City workers would never have been exploited if they were part of a union.
Smith's City has been asked to reimburse numerous staff for making them attended unpaid pre-work meetings.
Several other major retailers and supermarkets now face similar claims.
Workplace Relations Minister Iain Lees-Galloway says Smiths City took advantage of its workers.
"If they were Unionised, their union delegates would have picked up on it.
"There's no way that kind of behaviour would have carried on for as long as it has, if those workers were in union."
LISTEN ABOVE AS IAIN LEES-GALLOWAY SPEAKS WITH LARRY WILLIAMS