The blue-chip FTSE 100 index, which had risen to a 15-year high of 6,921.32 points on Wednesday, fell 0.1 percent to 6,888.90 points.

Centrica was the worst-performing FTSE 100 stock in percentage terms, dropping by 8.5 percent. Weak energy prices hit its annual profits and the company also disappointed by slashing its dividend.

"Centrica is another energy company that is suffering from a low oil price. Also, the fact that they've cut their dividend by such an amount will mean that some investors will now look elsewhere for better yields," said Dafydd Davies, partner at Charles Hanover Investments.

Oil prices tumbled on Thursday as U.S. inventories were expected to hit record highs, which put further pressure on energy stocks including Tullow Oil and BP.

BAE Systems rose 0.7 percent amid optimism over U.S. military spending next year, which traders said outweighed a company forecast of only a modest rise in earnings.

Aerospace and defence firm Rolls Royce rose 2.9 percent after a year of underperformance.

Babcock fell 5.7 percent after missing out on a military contract which Britain said it would award to Leidos Holdings.

Investors also remained cautious due to uncertainty over Greece's efforts to secure a new debt deal.

Greece formally requested a six-month extension to its euro zone loan agreement on Thursday, offering concessions as it sought to avoid running out of cash within weeks but running into strong objections from Germany.

The FTSE turned sharply negative after the response from Germany, and traders were cautious over the prospect of a near-term solution to the impasse.

Deutsche Bank said some sort of agreement was still its baseline scenario ahead of a meeting of euro zone finance ministers tomorrow.

"Assuming an agreement is indeed reached, it is important to point out that this will only mark the very first step in what is still a long road to resolution to the Greek crisis," George Saravelos, strategist at Deutsche Bank, said.

"On the positive side, a potential 'agreement' tomorrow will provide a little breathing room to the Greek financial system."

(editing by John Stonestreet)

By Sudip Kar-Gupta and Alistair Smout