Debenhams said on Friday it was seeking 200 million pounds of additional funds from lenders, allowing it to pursue restructuring options to secure its future. It said some options would wipe out shareholders.
Sports Direct, controlled by founder and Chief Executive Mike Ashley, is Debenhams' largest shareholder with a near 30 percent stake.
"If guidance as to what might represent a workable solution for Debenhams could result in no equity value for Debenhams' current shareholders, from Sports Direct's perspective and that of Debenhams' wider stakeholders, that is not a workable solution," Sports Direct said.
Sports Direct called on Debenhams to reconsider the offers of assistance it had made to the group, which included a 150 million pound loan and the purchase of Debenhams' Danish business Magasin Du Nord for 100 million pounds.
(Reporting by James Davey; Editing by Edmund Blair)