British supermarket chain Sainsbury's revealed Tuesday that sales slumped in its fourth quarter, breaking a nine-year run of underlying growth, and warned over the challenging outlook. Sales excluding fuel on a like-for-like basis -- stripping out the impact of new floor space -- dived 3.1 percent in the ten weeks to March 15, Sainsbury's said in an update. That was the group's first drop after 36 straight quarters of sales growth, and marked a sharp reversal in fortunes as it prepares for the exit of chief executive Justin King. The performance contrasted with an increase of 3.6 percent in the corresponding period of the previous financial year. "We have seen a decline in sales in the quarter reflecting tough comparatives. This time last year our sales benefited significantly from the discovery of horsemeat in some branded and competitors' products," said King. He added: "Although some economic indicators are showing an improvement in the health of the economy, we expect the outlook for customers to continue to be challenging for the coming year." The group's fourth-quarter performance was hit by the later timing of Easter and Mother's Day, which fall in the first quarter of the group's 2014/2015 financial year. The company had meanwhile announced earlier this year that King will leave the group in July after a decade at the helm. He will be succeeded by Mike Coupe, who is currently commercial director.