In results to April 2, M&S said that its food sales, although up 2.4% on last year to £3,509.7m, were down 2.6% on a like-for-like basis.
However, the retailer said that it would be looking to its Simply Food format stores to reverse this trend following the success of the 30 stores that opened last year.
The group will open eight pilot Simply Food stores on BP Connect forecourt sites this year, with the first of these stores to open by autumn this year.
A further 20 Simply Food stores are expected to open in 2005-2006.
UK retail sales slipped 1.7% to £7,034.7m from £7,159.8m last year and on a like-for-like basis fell 5.1%.
Group profits before tax and exceptional items also slumped 19% to £618m from £763.2m last year.
M&S said that although it had made good progress “there remains much to do”, with tough and economic competitive conditions expected to continue.