The benchmark index finished up 0.1 percent at 6,270.79 points, a fourth straight day of gains. The commodity-heavy index rose nearly 2 percent this week, buoyed by an oil price rally to more than $50 a barrel for the first time this year, as well as a rise in banks.

Shares in Royal Mail rose more than 2 percent, the top gainer in the FTSE 100 index, with traders saying that the stock was helped by a read-across from a report of a possible merger between Belgian and Dutch mail operators Bpost and PostNL.

Royal Mail was also buoyed by news that the Unite employees union had cancelled its proposed strike action. The news followed this week's ruling from Britain's telecom regulator Ofcom saying it would not impose new price controls on the company's wholesale or retail products, citing the declining letters market and increased competition in parcels.

"Royal Mail is rounding out the session at the top of the pile, with that mid-week ruling by Ofcom evidently still delivering for the firm," Tony Cross, analyst at Trustnet Direct, said. "It’s the miners who are struggling once again."

The UK mining index fell 1.3 percent amid lingering concerns about global metals demand. Shares in Anglo American, Antofagasta and BHP Billiton declined 1.4 to 2.7 percent.

Energy shares also fell as oil markets slipped around 1 percent, retreating from seven-month highs, as traders weighed the prospect of crude production intensifying because of prices near $50 a barrel. [O/R]

The UK energy index fell 0.6 percent, dragged down by a 0.7 percent and 0.5 percent fall in BP and Royal Dutch Shell respectively.

"We've had a decent move upwards over the last week or so, helped by the rise in crude above 50 bucks. But if some of these commodity-related stocks and financials start to tail back off again, then the overall market could drift heading into the weekend," TJM Partners head of trading, Manoj Ladwa, said.

(Editing by Mark Heinrich)

By Atul Prakash and Alistair Smout