Sports Direct, which has a near 30 percent stake in Debenhams, did not say how many Debenhams shareholders were backing it or name any of them.
Last year Sports Direct bought department store chain House of Fraser out of administration and has been trying to wrest control of Debenhams for months.
Sports Direct said it has set up a template letter on its website to enable any shareholders in Debenhams to make their views known.
On Friday Debenhams secured 200 million pounds ($261.4 million) in new funds but warned shareholders still faced being wiped out unless Sports Direct gave its support.
Debenhams said Sports Direct needed to either make a firm offer for the group, underwrite a rights issue, or provide debt funding if it wanted to prevent Debenhams' ownership falling into the hands of lenders.
Sports Direct said last week it was considering a 61.4 million pound offer.
(Reporting by James Davey, editing by Louise Heavens)