A US judge has ruled BP made "profit-driven decisions" during the drilling of an oil well in the Gulf of Mexico that led to a deadly explosion.
Ruling that BP had acted recklessly in relation to the 2010 spill, District Judge Barbier said: "These instances of negligence, taken together, evince an extreme deviation from the standard of care and a conscious disregard of known risks."
The oil giant pleaded guilty in January 2013 to manslaughter charges for the deaths of 11 rig workers following the blast.
A ruling of gross negligence against BP in relation to the Gulf of Mexico oil spill is an "unambiguous warning" to the US government and the oil industry, Greenpeace says.
The campaign group added that if drilling in the temperate conditions of the Gulf of Mexico could not be done safely, plans submitted for approval by Shell to operate in the Alaskan Arctic "would be disastrous".
A reminder of the timeline of events in the Gulf of Mexico oil spill:
- 20 April 2010: Explosion and fire on Deepwater Horizon rig kills 11 workers and injures 17. The rig is owned by Transocean Ltd and licensed to BP.
- 22 April: Rig capsizes and sinks, leading oil to discharge through the gulf.
- 30 April: Then BP boss Tony Hayward says company accepts responsibility for the spill and promises to compensate all those affected.
- 22 June: After receiving criticism for his handling of the crisis - including comment he would like his life back - Hayward hands day-to-day reponsibility for spill operations to Managing Director BOB Dudley - later named as next CEO.
- 29 September - BP permanently seals the leaking well.
BP claims 3.26 million barrels leaked from the well in total, while the US government puts the spillage at around 4.9 million barrels.
BP says it plans to appeal a US court's ruling that it was grossly negligent in the lead up to the Gulf of Mexico oil spill.
The Court is yet to rule on the number of barrels spilled, which will be key in determining the fine it orders BP to pay.
BP will also seek to show that its conduct merits a penalty below the maximum applicable, the company said in its statement.
BP shares appear set for their worst one-day fall since 2010 after a judge ruled the oil company had been negligent in events leading up to the 2010 Gulf of Mexico oil spill.
The company's shares were down by 6% at the close of trading in London - making it the worst performer on the FTSE 100.
The ruling could add billions of dollars in fines to the more than £25 billion the company has already been charged for the disaster.
A US judge has said that BP's reckless conduct led to the Gulf of Mexico oil spill, in a ruling that may cost the company billions.
Downing Street said that Mr Cameron has not spoken with BP about their concern about the rising compensation costs from the 2010 Gulf of Mexico oil spill, nor did he raise the issue with president Obama or other US authorities during his visit last week. A Number 10 spokesperson said:
British Petroleum has warned that millions of dollars of "fictitious" compensation claims for the 2010 Gulf of Mexico oil spill are putting the company at risk.
BP has sought an injunction to stop payouts to US companies it argues are claiming fraudulent or inflated losses from its £5.4 billion compensation pot.
An appeal document by the group argues that businesses in the US have been handed millions of dollars for "non-existent, artificially calculated losses", according to reports.
BP warned in the court filing that it will be "irreparably harmed" unless the compensation system is reformed.
British Petroleum has urged David Cameron to step in over the company's rising compensation costs for the 2010 Gulf of Mexico oil disaster, according to the BBC.
The company feels its financial recovery is at risk due to these costs and BP also worry that they could become a takeover target, the report says.
BP, who reportedly feel the compensation system is being abused, has urged the Prime Minister to bring up this issue with the US government, the BBC suggests.
The 2010 disaster killed 11 oil rig workers and around four million barrels of oil poured into the Gulf of Mexico.
In 2012, BP agreed to pay £5.4 billion in compensation but the company now expects that cost to be higher.
Passengers who are among 4,200 people on board a stranded cruise ship in the Gulf of Mexico have said conditions on the vessel "are getting worse by the hour".
Cabin carpets on board the Carnival cruise ship, which is being towed by a tug boat after being halted Sunday because of a fire in the engine room, are now soaked in urine, according to those on board.
Many have been forced to sleep in tents on deck and food supplies have been reduced to cold onion sandwiches, the passengers reported via a patchy phone line.
The ship is being towed to Mobile, Alabama, at the rate of a few miles per hour. It is expected to reach land on Thursday.