Marks & Spencer will continue to struggle against the big four over the next year, a report from research group Bernstein warns.

Growth in M&S' food division slumped from 20% in 2006 to -8% at the end of 2008. Sainsbury's and Tesco are picking up the most M&S customers, followed by Morrisons and Asda.

The Bernstein report said that in addition to M&S' premium positioning working against the brand, its narrow range meant most shoppers used it as a 'top-up' shop that was easy to cut out as consumers look to save cash.

Aggressive promotional activity is the only short-term solution for Marks & Spencer, Bernstein advised, though this would impact on the retailer's 33.9% gross margin. In the longer term, logistical improvements, a shift to convenience and working to build customer traffic would reinvigorate the division.