* FTSE 100 sheds 0.4 percent
* Banks lead fallers after British Q4 GDP data
* Diageo lifted by further positive broker comment
LONDON, Jan 25 (Reuters) - Britain's top share index fell on Tuesday, weighed down by banking stocks and retailers, as investors worried over the UK economy after a shock 0.5-percent contraction in GDP in the last three months of 2010.
By 1216 GMT, the FTSE 100 was down 20.82 points, or 0.4 percent, at 5,923.03, retreating after gaining 0.8 percent in the previous session.
Economists had only expected growth to slow to 0.5 percent after 0.7 percent growth in the third quarter, though uncertainty over the impact of December's snow disruption meant the range of forecasts was wide.
Market watchers said the weak data reinforced concerns about whether economic recovery will be sustained when the government accelerates a programme of deep public spending cuts.
"It poses a real threat Britain could go into a double-dip recession, particularly if the austerity measures slow growth more excessively than the government are predicting," Joshua Raymond, market strategist at City Index, said.
"It's just hampered a bit of appetite for risk," he said.
Banks were the biggest drag on the blue chip index, with part-nationalised lender Lloyds Banking Group the worst off, down 2.6 percent.
Global lender HSBC, however, bucked the weak sector trend, adding 0.4 percent.
Retailers were also out of favour, with Next among the top FTSE 100 fallers, as the GDP data created concerns about consumers' willingness to spend.
MINERS WEIGH
Miners were out of favour. African Barrick Gold and Randgold Resources were among the worst off, down 2.9 percent and 2.5 percent respectively, after the price of gold hit a 10-week low.
Precious metals processor Johnson Matthey rallied, up 1.6 percent, helped by improving sales trends in the automotive industry for which it manufactures catalytic convertors, traders said.
BG Group added 0.6 percent. The company is to invest $10 billion in Brazil over the next decade as it seeks to accelerate development of the country's deepwater oil fields, the Daily Telegraph reported.
Drinks group Diageo took on 0.7 percent supported by further positive broker comment and figures for the U.S. spirits industry.
Morgan Stanley raised its target price for Diageo, with Exane BNP Paribas having done the same on Monday.
U.S. stock index futures pointed to a lower opening on Wall Street, with BlackRock, Yahoo, Johnson & Johnson, DuPont, and Harley-Davidson among companies reporting results on Tuesday. (Editing by Jon Loades-Carter)