Marks & Spencer (M&S) has seen profit before tax down £122.6m on last year, despite strong like-for-like food sales.

The retailer achieved profit before tax of £658.0m (2011: £780.6m) in the full year to 31 March 2012. Underlying profit before tax was £705.9m, down from £714.3m last year.

Its total food sales in the UK were up 3.9%, with like-for-like growth of 2.1%. Overall group sales increased 2% to £9.9bn.

M&S said it had improved the quality of many of its existing products during the year, without increasing price. For example it upped the prawn content of its prawn mayo sandwich by 40%, which increased sales by 21%.

In its 15 pilot stores launched last November, which feature new-style artisan bakeries, sales have been 2.5% ahead of the control group in the first six months of trading.

Marc Bolland, chief executive, said that while the economic environment had deteriorated since M&S first set out its strategic plans, “we have made significant progress”.

“Our UK pilot stores are delivering good results, which has given us the confidence to launch phase two of the programme. We are well on track to become a truly international multi-channel retailer.

“By the end of this year we will be transacting from 10 websites worldwide and opening around 100 international stores per year.”