The FTSE 100 Index has closed down 38.4 points at 5127.6.
The move down was led mainly by tech shares as a downbeat outlook from US chip giant Intel did little for confidence.
ARM Holdings took the brunt of the warning in London, falling more than 5% - down 18p at 325½p.
Others in the tech sector heading south included the Logica and Sage - down 40p to 604p and 12¼p to 240¼p respectively.
Other stocks under pressure in London included Vodafone, down 2¼p at 162½p, BT Group off 5p at 241¼p and mmO2, down 1½p at 86½p.
Fortunes for retail shares were also mixed despite another bright session for Christmas trading reports.
Marks & Spencer made early gains as the firm showed its recovery was on track with sales growth of 8.3% in the seven weeks to January 12. But it couldn't hold on to its early rise in the City and closed fractionally down - off half a penny at 359½p.
A number of other retail stocks lost their sparkle as the day wore on, with Great Universal Stores down 1½p at 640p and Next off 17p at 905p.
Tesco also lost 4¾p at 233p but rivals Sainsbury's and Safeway both gained as the City digested trading statements from the sector earlier this week.
Sainsbury's lifted 9½p at 385p, while Safeway rose 3½p at 310½p.
Among smaller retail stocks Matalan rose 7½p to 374p and Debenhams gained 2¼p at 382p.