The Sports Direct tycoon controls the merchandising arm of the company, thanks to an agreement made with former chief executive Charles Green.
Rangers latest claim is said to regard the manner in which club trademarks were used prior to the current board regaining legal ownership back in February earlier this year.
Details were found in the Rangers Retail annual report which suggested £1m may be payable to Rangers over a breach of terms.
However, Sports Direct insist there is “no credible basis” for any claim and that they will “fully defend itself against any allegations”.
Rangers have said in the past they are continuously working to terminate, or at least renegotiate, the deal over Rangers Retail.
They moved to terminate the joint venture earlier this year, though it has a seven-year notice period.
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