The FTSE 100 was down 1.1 percent to its lowest in more than two weeks, underperforming its European peers. The FTSE 250 was down 0.1 percent by 0825 GMT.

Precious-metals miner Fresnillo slid 10.6 percent to the bottom of the main index. Pretax profit for the year slumped by more than a third and it flagged an "unwelcome degree of uncertainty" from the China-U.S. trade dispute.

The pound gained on reports that UK Prime Minister Theresa May would formally rule out a no-deal Brexit and delay the March 29 deadline for UK's exit from the European Union.

That hit stocks that book much of their earnings in dollars, but it capped losses in the more domestically focussed mid-cap index. British American Tobacco led the fallers and gave up 2.3 percent.

British Airways owner IAG slipped 3.3 percent after reports that it would no longer be part of MSCI global standard indexes.

Standard Chartered fell 2.5 percent after it reported 2018 results and said it would cut costs and quit smaller businesses as part of a new strategy.

"We continue to believe that the revenue target is a challenge, particularly given commentary that YTD 2019 revenue has started down on 2018," Jefferies analysts said.

Travis Perkins surged 11 percent after its full-year adjusted pretax profit beat expectations.

Speciality chemicals maker Croda fell nearly 4 percent after its annual pretax profit missed estimates and it said it was stockpiling goods ahead of Brexit.

Mid-cap engineering company Meggitt gave up 6 percent after a weak organic revenue growth forecast.

Babcock skidded 4.2 percent after it said restructuring its European business for Brexit would 10 million pounds ($13 million) a year.