Union leader Steve Turner has called for the government to crack down on zero hours contracts.
His comments come after Sports Direct owner Mike Ashley agreed to attend questioning from the Business, Innovation and Skills Committee about working conditions, including zero hours contracts.
However, he claims he will only attend on the condition MPs visit his main warehouse beforehand to view working practices. The billionaire has also offered to fly the MPs to the location in Derbyshire in his helicopter.
But Turner, the assistant general secretary at Unite, has called for zero hours contracts to be changed by the government.
"They've done it successfully in New Zealand," he told Julia Hartley-Brewer. "There's no reason not to commit to employees for guaranteed hours each week, and then to offer alternatives like additional hours.
"Zero hours contracts are used as a mechanism of control, so there are no disciplinary procedures. If you step out of line, or you don't look right, you could have half as many hours the next week."
The trade unionist hopes Ashley will appear before the parliamentary committee in order to make a start on changing the contracts.
"Sports Direct is the main benefactor of [zero hours contracts]," he added. "There is an opportunity to have a serious debate about the future of work, and the provision of decent work.
"If we don't stop [zero hours contracts] it will become the norm, and I see many people who feel their only hope of employment is in one of these forms of exploitive contract."