The FTSE 100 Index is down 15.5 points at lunchtime at 5278.1.
Retailers are suffering on the stock market, despite a swathe of good news about bumper Christmas trading.
A number of investors are taking profits amid worries that the good times on the high street could soon be over.
Next's share price is down 3% or 26p to 909p despite it posting strong like-for-like sales growth of 9% over the 23 weeks to January 5.
Dixons, which reports interim results tomorrow, is down 9p to 237¾p; Marks & Spencer is 4½p lower at 363p; GUS is down 12½p to 667p; and Boots is off 6p at 593p.
Among the FTSE 250 stocks on the slide are Woolworths, off 2¾p at 43p; JJB Sports, down 24½p at 418½p; and Debenhams, off 17¼p at 379¾p.
EasyJet is down 5½p to 484p despite releasing healthy passenger numbers for December, showing it carried 670,390 passengers - up 36.5% year-on-year.
Rival low-fares airline Ryanair has also seen its share price fall, and is down 3½p to 428p.
But Anglo-Australian logistics group Brambles is up 11p to 365p after a positive note from stockbroker Morgan Stanley.
Abbey National is up 16½p to £10 after the City warmed to its decision to increase the amount of interest paid on current accounts to 3%.