Mining stocks have come under more pressure as the prospect of a reduction in US stimulus efforts casts uncertainty over the global outlook.
All eyes were on the publication of minutes of the latest meeting of the US Federal Reserve later in the session, with investors expecting a clearer insight into when the Fed plans to taper quantitative easing (QE).
Markets have been derailed by the QE speculation, with some commentators fearing that such a tapering move could come as soon as next month.
The FTSE 100 Index was down by another 44.5 points to 6408.9, having lost around £60 billion since the start of August. Three months ago, the FTSE 100 reached 6840.3, its best result since the dotcom boom in December 1999.
Miners have suffered on fears the Fed's actions will trigger a drop-off in global demand, particularly in emerging markets. BHP Billiton was among the fallers, with a decline of 44p to 1879.25p, while Antofagasta slipped 14.5p to 897.5p.
Commodities trader Glencore Xstrata bucked the trend as investors returned to the stock in the wake of a big fall yesterday, when sentiment was hit by a £5 billion write-down on the value of its recent Xstrata acquisition.
Glencore shares were 4.8p higher at 301.9p, although the FTSE 100 stock still trailed the session's strongest performers, Standard Life and ITV.
The broadcaster was 2.6p higher at 164.5p after a positive read-across from results from Scottish commercial station STV, which posted a 5% hike in underlying pre-tax profits to £6.7 million and reported further momentum in its expanding digital and production operations.
STV was 10.5p higher at 184.5p as it revealed plans to resume shareholder dividend payments for the first time in seven years.
Standard Life led the FTSE 100 risers board, up 6.6p to 349.5p, after Bank of America Merrill Lynch upgraded the stock to neutral from underperform.
There was little in the way of major corporate news to excite traders, although Lloyds Banking Group was 0.2p higher at 74p after offloading its German insurance business Heidelberger Leben in a £250 million deal.
The taxpayer-backed bank will take a £330 million loss on the transaction but the removal of the insurer from its books will boost Lloyds' capital position by £400 million.
Cooker firm Aga Rangemaster was higher, up 6p to 109.75p, as it showed signs of benefiting from the house market upturn.
Half-year operating profits were flat at £1.5 million but chief executive William McGrath said the mood among customers was better and that there was a "buzz" about the company's new products.