LONDON - A drop in oil major BP accounted for a modest opening fall by Britain's top share index on Wednesday as the Gulf of Mexico oil spill nightmare returned to haunt the British group.

The US Justice Department is ramping up its rhetoric against BP for the massive 2010 oil spill in the Gulf of Mexico, describing in new court papers examples of what it calls “gross negligence and wilful misconduct”.

BP's shares shed 3 percent, knocking over 10 points off the UK blue chip index in strong early volume of 18 percent of the stock's 90-day daily average in the first 10 minutes of trading.

By that time, the FTSE 100 index was down 2.10 points, or 0.1 percent at 5,669.91, steadying slightly after sliding 1.5 percent lower in the previous session, with investors bracing themselves for the outcome of a key European Central Bank meeting on Thursday. - Reuters