Some of the biggest fallers - Vodafone, Imperial Brands, DCC, National Grid and Evraz - went ex-dividend, taking around 9.8 points off the index.

The FTSE 100 was down 1.4 percent at 1028 GMT, handing back the previous session's gains and underperforming its euro zone counterparts as the pound surged on positive news from Brussels midmorning.

The FTSE 250 was down 0.8 percent. With US markets closed, volumes were lower than usual.

"The drop has taken some of the shine off yesterday's surge in risk assets, although it will be worth watching to see if any buyers follow up on this morning's weakness and help to set us up for a better end to the month and a more optimistic start to December," said IG chief market analyst Chris Beauchamp.

Energy, mining and consumer staples accounted for the majority of the losses.

Fresnillo was the biggest faller, down 10.5 percent, after Morgan Stanley downgraded the stock on fears the company will find doing business in Mexico much harder following the passage of recent legislation.

Utilities were also in focus after earnings from Centrica and Severn Trent.

Centrica hit March lows and was on track for its worst day in a year after the energy supplier reported losing customers, lower nuclear power generation and a fall in output at its oil and gas division. Severn Trent dropped 1.7 percent after its results.

Among the mid-caps, Rotork slumped more than 7 percent to the bottom of the index as investors focused on the drop in its third-quarter order book, rather than the in-line set of results. Investec analysts say the shares look overvalued based on their earnings outlook.

Hill & Smith rose 3.5 percent after confirming its full-year earnings outlook, with third-quarter organic underlying revenue growth of 5 percent and activity levels healthy after the tough first quarter.

"The Q3 update is reassuringly inline, confirming that the company has been performing well since the weather-related issues in Q1," said Peel Hunt analysts.