(Fixes typo in name Royal Dutch Shell in line 54)
* Banks fall; weak UK data adds to negative tone
* Resources stocks hit by weak metal, crude prices
* Defensive pharmaceuticals, tobaccos, beverages gain
By Jon Hopkins
LONDON, Sept 1 (Reuters) - Britain's top share index shed 1.8 percent on Tuesday, dragged back by weakness in banks and commodity issues as doubts about the sustainability of this summer's strong rally emerged on the first day of September.
At the close, the FTSE 100 was 89.20 points lower at 4,819.70 after ending 0.8 percent higher on Friday, when it also touched a near 11-month high.
Britain's blue-chip index gained 6.5 percent in August and is up around 40 percent since hitting its lowest level in more than six years in March.
"The overriding concern of this recent rally has been its lack of volume and today may have marked the first round of sustained profit taking," said Angus Campbell, head of sales at Capital Spreads.
"In the back of many investors' minds is the concern that September is usually a poor month for equities and we haven't got the month off to the best of starts," Campbell added.
Cyclical stocks, more sensitive to resurfacing fears over the global recovery were weaker as a sharp sell-off by global equities on Monday, when London markets were closed for a public holiday, filtered through to the UK market.
Banks were the biggest drag on the blue-chip index, with HSBC, Lloyds Banking Group, Barclays, Royal Bank of Scotland, and Standard Chartered losing between 1.9 and 4.8 percent.
Also among weak financials, RSA Insurance shed 4.8 percent as a report of a rights issue to raise up to $1 billion unsettled investors and surprised analysts, who said they saw no need for a cash call. Peers Legal & General and Prudential fell 3.3 and 2.1 percent, respectively.
Weak UK data reinforced the more negative tone at the start of the month, with Britain's manufacturing sector dipping unexpectedly in August and net lending to Britons falling at its sharpest rate since records began in 1993.
U.S. blue chips were 1.7 percent lower by London's close as an early rally following some upbeat data was reversed as financials took a tumble.
A survey showed the U.S. manufacturing sector returned to growth in August after a prolonged slump, while pending home sales raced to a two-year high in July.
Commodity issues were hit by softer metal and crude prices as demand concerns re-emerged with global recovery worries.
Eurasian Natural Resources, Vedanta Resources, Lonmin, Anglo American, Xstrata, and Antofagasta fell 4.0 to 6.9 percent.
BP, Royal Dutch Shell, BG Group, Cairn Energy, and Tullow Oil, up 0.6 percent, lifted by trial results for its experimental blood thinner Brilinta.
Goldman Sachs also raised its price target for AstraZeneca.
Peer Shire gained 0.1 percent.
Household products, beverage, and tobacco stocks were also in demand as investors homed in on stocks they expect to hold firm in a still-challenging economic environment.
Reckitt Benckiser was the top FTSE 100 riser, up 1.0 percent, while Diageo took on 0.9 percent, and British American Tobacco gained 0.8 percent.
"Investors will take a long hard look at the rally over August, and when we see a move back to risk aversion, there's a move back into defensives," said Richard Hunter, head of equities at Hargreaves Lansdown. (Additional reporting by Simon Falush; editing by Rupert Winchester)