London's top-flight index sunk deeper into the red as it came under pressure from sliding commodity stocks and a slump from the supermarkets.
The FTSE 100 index fell 73.6 points to 6112.02, as the falling copper price and a slip in Brent crude took its toll on the mining sector.
Glencore was 4.8p lower at 145.1p, while Anglo American tumbled 22.5p to 643.2p, as the price of oil dropped 0.3% to 44.83 US dollars a barrel.
Commodity stocks also bore the brunt of Tuesday's manufacturing update from China, which showed activity shrank for the 14th month in a row in April, sparking investor concern that its consumption of commodities will begin to fall.
Sainsbury's was more than 6% down after it reported a hit to annual profits triggered by the long-running supermarket price war.
The retailer - which last month won a four-month takeover tussle to snap up Argos owner Home Retail for £1.4 billion - booked a 13.8% drop in underlying annual profits and a 0.9% fall in like-for-like sales.
Rival Tesco also saw it share price tumble after the latest industry report from Kantar Worldpanel showed its market share had fallen to 28%, down 0.4% in the 12 weeks to April 26, while sales fell 1.3% to £7.12 billion.
Shares were down more than 5% or 9.2p to 160.1p.
Across Europe, the Cac 40 in France was 1.1% lower, while Germany's Dax fell just under 1%.
The pound was down 0.3% against the dollar at 1.448, as growth in the UK's construction sector slowed to its lowest level for almost three years in April amid ''clouds of uncertainty'' ahead of the EU referendum.
The Markit/CIPS construction purchasing managers' index (PMI) showed a reading of 52 last month, down from 54.2 in March and the weakest since June 2013. A reading above 50 indicates expansion.
Sterling also fell 0.3% against the euro at 1.260.
In stocks, Sainsbury's slipped 17.9p to 267.8p, as it posted underlying pre-tax profits of £587 million for the year to March 12, down from £681 million a year earlier.
But on a bottom-line basis, it swung out of the red with pre-tax profits of £548 million against losses of £72 million the previous year, which marked the company's first loss in a decade.
Oil giant Shell was 39p lower at 1722.5p, as its first-quarter profits slumped 58% to 1.6 billion US dollars (£1.1 billion), with the falling price of Brent crude continuing to hammer the sector.
The London Stock Exchange (LSE) also fell heavily - down 113p to 2576p - after the owner of the New York Stock Exchange, the Intercontinental Exchange (ICE), said it would not pursue a takeover.
The move paves the way for a £20 billion merger between LSE and Germany's Deutsche Borse, which ICE had threatened to gatecrash.
However, investors cheered a trading update from high street bellwether Next despite a warning that its full-year profits could take a hit after sales for the first quarter fell 0.9%.
Sales at the chain's high street shops plunged 4.7% as it pointed to March and April's cold weather dampening demand for its clothing.
The company also said the lacklustre figures could indicate a wider slowdown in consumer spending.
Shares were up more than 3% or 172p to 5150p.
The biggest risers in the FTSE 100 Index were Next up 172p to 5150p, Admiral Group up 25p to 1928p, Direct Line Insurance Group up 2.7p to 371p, and Provident Financial up 18p to 2942p.
The biggest fallers were Rangold Resources down 775p to 5830p, Sainsbury's down 17.9p to 267.8p, BHP Billiton down 50.5p to 824.8p, and Tesco down 9.2p to 160.1p.
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