The company's two supply agreements with Morrisons accounted for 78% of its turnover in the financial year to 31 March 2010.
MBL Group's board said it had been negotiating with Morrisons for "several months" to strike a new logistics deal but talks had been unsuccessful. The contract was won by rival Cinram instead. Morrisons is also understood to be buying more entertainment products directly from suppliers.
Finance director Steven Walsh-Hill will leave MBL immediately as the hunt begins for a buyer and "significant" job cuts are now regarded as inevitable.
MBL Group has supplied Morrisons for 14 years.