The FTSE 100 index <.FTSE> fell 0.8 percent to 6,114.88 points by 1455 GMT, reversing oil-related gains made earlier on in the session.

Mining companies were the top fallers on the blue chip index, with Anglo American (>> Anglo American plc), Antofagasta (>> Antofagasta plc), BHP Billiton (>> BHP Billiton plc), Rio Tinto (>> Rio Tinto plc) and Glencore (>> Glencore PLC) all falling between 2.7 percent and 7 percent.

Analysts cited a note by UBS which questioned whether investors had seen the 2016 peak for miners, as April data from China, the world's biggest consumer of metals, proved lacklustre.

"The first quarter was very decent for (the miners) but a lot of it has been on speculation and that was bargain hunting," Brenda Kelly, head analyst at London Capital Group, said.

The British mining sector <.FTNMX1770> has fallen 20 percent below a year high reached in April, although it is still up 20 percent so far this year.

Companies trading ex-dividend also fell, including Britain's largest energy supplier, Centrica (>> Centrica PLC), which was down 2.9 percent. Sainsbury's (>> J Sainsbury plc), GlaxoSmithKline (>> GlaxoSmithKline plc) and Morrisons (>> WM Morrison Supermarkets PLC) were also down 1.4 to 4.2 percent.

ITV (>> ITV plc) fell 2.6 percent, taking this month's losses to around 6.8 percent. The commercial broadcaster said companies were holding back from buying advertising before next month's referendum on whether Britain should remain a member of the European Union, prompting it to lower its forecast for first-half ad revenues.

"In periods of economic uncertainty, advertising budgets are usually the first to fall foul of spending cuts as companies become less certain on prospects," said Richard Hunter, head of research at Wilson King Investment Management

"This uncertainty, coupled with the broader debate on the future of free-to-air broadcasting, has resulted in the shares missing out on the recent market recovery."

Caterer Compass Group (>> Compass Group plc) was the top gainer, rising 1.7 percent after brokers RBC Capital Markets and Natixis raised their target prices for the stock. The gains recouped losses from the previous session after the company posted results.

"H1 results highlighted the high growth and resilience of the Compass business model. Whilst the stock has performed strongly, we believe the premium valuation is warranted. Compass remains a sound equity story in our view," Andrew Brooke, an analyst at RBC Capital Markets, said in a note.

Gold miners were also in demand, with investors betting on the continuity of a rally in gold prices. Shares in Randgold Resources RRS.L and Fresnillo FRES.L rose 1.4 percent and 0.3 percent respectively.

Packaging and paper company Mondi (>> Mondi Plc) advanced 0.4 percent after reporting first-quarter underlying profit rose 14 percent on strong performances in consumer packaging and uncoated fine paper and better sales in South Africa.

(Reporting by Atul Prakash; Editing by Andrew Roche)

By Kit Rees and Atul Prakash