* FTSE falls 1.1 percent, touches lowest since May 5
* Miners weaker as confidence in demand for metals ebbs
* Pharmaceuticals stocks gain ground; BT top riser * Sainsbury slides after capital raising
By Simon Falush
LONDON, June 17 (Reuters) - Britain's top share index fell 1.1 percent by midday on Wednesday as commodity stocks fell back, dented by a retreat in energy and metal prices and as investor confidence in the state of the global economy waned.
By 1044 GMT the FTSE 100 was down 48.16 points at 4,280.41, touching its lowest since May 5, having closed 2.56 points higher at 4,328.57 in the previous session.
Miners were the biggest drag on the index as metal prices were stuck well below the highs since late last year struck last week as hopes the global economy was set for a sharp rebound faded.
Rio Tinto, Kazakhmys, Eurasian Natural Resources, Anglo American, Lonmin and BHP Billiton fell 3-7.4 percent.
"We've had an aggressive move to the upside and there's profit taking going on as it looks as though the rally has moved too far too fast," said Henk Potts, strategist at Barclays Wealth.
The blue-chip index is down 3.4 percent for the year but is still 23.7 percent above a six-year trough set on March 9.
"There are still plenty of reasons to be positive given low interest rates and unprecedented levels of stimulus from quantitative easing," Potts added.
"But there are still a lot of unanswered questions and investors will wait for tangible evidence before pushing the market higher."
Energy stocks were also a big drain on the index as crude fell back towards $70 per barrel.
BP, Royal Dutch Shell, BG Group, Tullow Oil and Cairn Energy fell between 0.3 and 2.7 percent.
Employment data that showed the jobless rate rose at a slower than expected rate in May did little to cheer investors.
The Bank of England's Monetary Policy Committee voted unanimously to keep interest rates at a record low of 0.5 percent and maintain its 125 billion pound ($203.3 billion) quantitative easing programme.
SAINSBURY'S SALE
Sainsbury was among the heaviest fallers, down 6.6 percent after Britain's third largest grocer said it plans to raise 445 million pounds ($732 million) to accelerate its expansion, as it posted first-quarter sales at the top end of expectations.
The move to place new shares and convertible bonds also dragged on peers WM Morrison and Tesco, which fell 1.3 and 1.7 percent respectively.
Defensive pharmaceuticals stocks were in positive territory with Shire leading the way, up 2 percent on expectations its drug Replagal will benefit from production problems at U.S. rival Genzyme.
This benefits Shire as it makes rival drug Fabrazyme.
BT Group was the top blue-chip gainer, up 3.2 percent supported by the British government's plans to impose a levy of 50 pence a month on copper phone lines.
BT is expected to take a leading role in the broadband expansion.
Finance minister Alistair Darling was set to warn the City to expect an increase in regulation and a crackdown on sloppy boardroom practices in the annual Mansion House speech, to be delivered on Wednesday evening, the Financial Times reported.
U.S. May CPI numbers will be the main macro focus later in the session, with a monthly rise of 0.3 percent expected, giving an annual decline of 0.9 percent, after a fall of 0.7 percent in April.
U.S. President Barack Obama will unveil plans on Wednesday for sweeping reform of financial regulation aimed at averting crises like the banking meltdown that has plunged the global economy into recession.
Severn Trent and United Utilities were heavy fallers, losing ground as they were among four stocks going ex-dividend. (Editing by Rupert Winchester)