Asda's sales slump 5.1 pct in a tough market for big four-Kantar Worldpanel

LONDON, May 4 (Reuters) - Sales at Wal-Mart's British supermarket chain Asda fell by 5.1 percent in 12 weeks to April 24, the worse performer in a period when all four of the biggest chains declined, Kantar Worldpanel said on Wednesday.

Sales at market leader Tesco were down 1.3 percent, ending four months of improvement, market researcher Kantar said, and Sainsbury's and Morrisons also posted falls of 0.4 percent and 2.6 percent, respectively.

(Reporting by Paul Sandle, editing by Louise Heavens)