The FTSE 100 Index is down 21.6 at 5113.7 at lunchtime.
Banking stocks are down after Barclays - itself off 4% or 24p at 596p - warned of higher costs and bad debt provisions in a statement ahead of its interim results in August.
Royal Bank of Scotland is down 33p to £19.70; Lloyds TSB is 11p lower at 739p; HBOS is down 12½p at 819½p; Standard Chartered has eased 9p to 809p; and HSBC is off 4½p at 839p.
The Footsie had made a 32 point gain in early trading as the City welcomed Vodafone's figures, despite huge bottom-line losses after the group incurred massive charges.
Investors focused on Vodafone's underlying performance, which showed strong profits growth before the one-off costs, but its share price is now up just 1¼p at 106¼p - having gained 7% at one stage.
Rival mmO2, which also surged during early trading, is now up just ¾p at 49¼p.
Sainsbury's is down 4p at 366¾p ahead of its annual results tomorrow; Safeway is down 6½p at 298½p; Morrisons has eased 6p to 220p; Tesco is down 3½p to 246p; and Marks & Spencer is off 5p at 386½p.
Durex condoms to Scholl footwear group SSL International is down 3% or 13½p to 377½p after reporting sharply lower full-year profits following action to solve problems with excess stocks.
But Hull-based Kingston Communications is up 1% or ¾p to 90p after saying it had enjoyed a 'solid' performance in the last year and was well placed to maintain growth.
New Look jumped 3% or 7½p to 273p after showing it had turned around its business, revamping its product and revitalising stores.