* Banks weighed on by Dubai debt exposure worries
* Commodity stocks under pressure
* Tesco down as Q3 sales growth disappoints
By Tricia Wright
LONDON, Dec 8 (Reuters) - Britain's top share index fell 1.6 percent on Tuesday, led down by banks on fresh worries over Dubai debt exposures and caution ahead of Wednesday's UK pre-budget report and with Tesco <TSCO.L> hurt by disappointing Q3 numbers.
By 1237 GMT the FTSE 100 index <
> was down 84.61 points at 5,226.05, near its lows for the session.Weakness in banking shares was the biggest drag on blue chip sentiment with investors concerned over their exposure to Dubai's debt, and worries about a possible windfall tax on banks being introduced by finance minister Alistair Darling in his pre-budget report on Wednesday.
Royal Bank of Scotland <RBS.L> slid 8.8 percent, also impacted by a WestLB downgrade to "sell" from "reduce", with HSBC <HSBA.L>, Barclays <BARC.L>, Standard Chartered <STAN.L> and Lloyds Banking Group <LLOY.L> down 0.8 to 3.5 percent.
"The weak German industrial output numbers ... and the size of losses facing Nakheel, a unit of Dubai World, have hit sentiment causing jitters across the market," said Manoj Ladwa, senior trader at ETX Capital.
Troubled Dubai property developer Nakheel made a first-half loss of 13.4 billion dirhams ($3.65 billion) as revenue fell and it wrote down the value of land and property, according to a report published on Tuesday. [
]Miners also weighed heavily on the blue chips. Xstrata <XTA.L> was among the hardest hit, down 2.4 percent after the firm said it is taking a $1.9 billion charge for restructuring its nickel business after metal prices fell, and is taking further charges of $545 million for copper smeltering operations in Canada and Chile. [
]Peers Eurasian Natural Resources <ENRC.L>, Lonmin <LMI.L>, Rio Tinto <RIO.L> and BHP Billiton <BLT.L> shed 1.1 to 2.7 percent.
Energy stocks were under pressure, hurt by a 0.4 percent drop in the price of crude <CLc1>, with Royal Dutch Shell <RDSa.L>, BP <BP.L> and BG Group <BG.L> off 0.4 to 1.6 percent.
"The market seems to have run out of steam generally," Ladwa said.
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Tesco shares lost 2.2 percent as the world's third-biggest retailer said sales at British stores open at least a year rose 2.8 percent, excluding gasoline sales and VAT sales tax, in the 13 weeks to Nov. 28.
That was slightly down on the 3.1 percent reported in the second quarter and shy of the average forecast of 3 percent in a Reuters poll of 12 analysts. [
]Other food retailers fell back on the news, with Sainsbury <SBRY.L> shedding 1.4 percent and Wm. Morrison Supermarkets <MRW.L> losing 0.7 percent.
Retail sales values rose at their slowest annual pace last month since August, held back by food sales where a fall in inflation led to their weakest performance in more than two years, a British Retail Consortium survey showed. [
]Media group Pearson <PSON.L> was the top FTSE 100 riser, up 1.8 percent after U.S. peer McGraw-Hill <MHP.N> said it expects a better year for all businesses in 2010. [
]Shares in WPP <WPP.L>, the world's largest advertising group, added 1.4 percent.
German industrial output unexpectedly fell in October, official data showed on Tuesday, pointing to a slowdown in the economy's recovery in the final quarter of this year. [
]British industrial output failed to grow in October, disappointing expectations for a further expansion and raising doubts over the strength of any recovery in the fourth quarter. [
]House prices, however, rose 1.4 percent month-on-month in November, according to the latest survey by the Halifax, much stronger than the 0.5 percent rise predicted. [
]The FTSE 100 index has gained about 51 percent from a six-year low hit in March, though it is still 3.3 percent below its level of mid-September 2008 before the collapse of Lehman Brothers. (Editing by Greg Mahlich)