OREANDA-NEWS. February 12, 2015. Britain's top equity index fell for a fourth straight session on Wednesday, with commodity shares losing ground after crude oil prices dropped and copper prices trimmed gains.

The UK Oil and Gas index fell 1.2 percent after crude dropped 3 percent on expectations of persistent oversupply, a stronger dollar and a report showing US crude stockpiles at a record high.

Oil and gas explorer Tullow Oil fell 8.6 percent, the biggest decline in the FTSE 100 index. The company reported a \\$2 billion pre-tax loss, its first in 15 years, and scrapped its final dividend payment.

"The stronger dollar has done its usual trick of knocking back commodity prices, taking commodity stocks with them," IG analyst Chris Beauchamp, said.

"It's hardly surprising to see such negativity in this sector, when we've China data that points this week to a continuing slowdown.

Oversupply and weak demand aren't going away, whether in oil or metals."

The mining index was down 1.8 percent as copper prices cut gains in afternoon trading session and nickel fell nearly 2 percent. Mining companies Rio Tinto and BHP Billiton were down 1.7 percent and 2.4 percent respectively.

The FTSE 100 was down 0.5 percent at 6,798.40 points by 1543 GMT. The index fell in the previous three sessions and headed for a weaker close on Wednesday.

Among other movers, Sky fell 2.5 percent after agreeing to pay 4.2 billion pounds to show 126 live Premier League football matches a season between 2016 to 2019, far outstripping forecasts.

"While arguably this should mean unchanged consensus numbers some investors are likely to de-rate the shares because of increased uncertainty around future content renewals and reduced future flexibility on costs," Barclays said.

However, BT rose 3.4 percent after securing 42 games a season for 960 million pounds, putting pressure on Sky to pay a premium.

ARM rose 3.9 percent after the British chip designer posted a 25 percent rise in fourth-quarter profit, more than expected.

Reckitt Benckiser Group rose 3.3 percent to touch a record high.

The British consumer goods maker said it was introducing a new cost-savings programme, noting that 2015 would be similar to last year.

Outside the blue-chips, British data centre provider Telecity Group rose 15 percent after saying it had reached a non-binding, all-share merger agreement with New York-listed Interxion.