Shares in BP fell a further 0.8 per cent this morning, having closed down 5.6 per cent yesterday, after U.S. District Judge Carl Barbier delivered a ruling against the oil giant which opens it up to further fines.

No fine was mentioned because the ruling did not provide specifics on how many barrels of oil BP actually spilt during the disaster, but estimates in the market are that the ruling could cost the company an extra $18bn (£11bn) in fines, on top of the $42bn it has already paid out.

Barbier ruled BP was mostly at fault and that two other companies in the case, Transocean and Halliburton, were less responsible for the disaster.

A surge of methane gas known to rig hands as a “kick” sparked an explosion aboard the Deepwater Horizon rig as it was drilling the mile-deep Macondo 252 well off Louisiana back in 2010, leading to a number of deaths and the subsequent oil spill.

BP said it “strongly disagrees” with the decision and will immediately appeal to the United States Court of Appeals for the Fifth Circuit.

“BP believes that the finding that it was grossly negligent with respect to the accident and that its activities at the Macondo well amounted to willful misconduct is not supported by the evidence at trial,” it said.

“The law is clear that proving gross negligence is a very high bar that was not met in this case. BP believes that an impartial view of the record does not support the erroneous conclusion reached by the District Court.”

It added during the penalty proceedings, BP will seek to show that its conduct merits a penalty that was well below the maximum allowed.