A survey conducted by retail consultancy Verdict Research found that Tesco sold £4.6bn of non-food products in 2004 while M&S sold £4.4bn.
The survey also predicts that the market share of grocers selling non-food products will increase to 12.7% this year with sales of £14.4bn.
Tesco, Sainsbury and Asda are also expected to sell more non-food products than the combined sales of all UK department stores by 2006.
The news is another blow to M&S which has been recently been embroiled in a damaging internal row over the appointment of a chairman.
The appointment of Lord Burns who will take up the position next year ended the row, but investors are now looking to the group to come up with a plan to raise sales which have fallen for the last six quarters.
M&S is also expected to announce the refurbishment of 20 stores at a cost of £300m.