The move reduces the potential fine under the Clean Water Act by $3.4bn.

BP is prepared for a court fight with US authorities over civil penalties for its role in the Gulf of Mexico oil spill, arguing that the fine it should face should be less than a quarter of the $20bn (£12.9bn) estimated by some analysts.

Following lengthy talks, the oil giant has indicated it does not expect to reach a settlement with the US Department of Justice ahead of its trial in America, which is due to start on February 25.

“In a way we are looking forward to the trial,” Rupert Bondy, BP’s general counsel, told the Financial Times.

“We have said all along we would be prepared to settle on reasonable terms, [but] we are prepared to go to trial.”

BP’s overall provision for the spill had included $3.5bn for fines under the Clean Water Act, although this could be dwarfed by the total possible fine of $20bn. BP has disputed the US authorities’ view of both how much oil was spilled and the level of negligence involved.

It strenuously denies a charge of gross negligence, which carries a maximum penalty of $4,300 per barrel spilt. Ordinary negligence carries a penalty of up to $1,100 per barrel.

“What is clear is that [gross negligence] is a very high bar, and we firmly believe the bar is not met in this case,” said Mr Bondy. He said that the actual range of penalties BP could face started “far far below” the $5bn often cited as the minimum possible.

BP had also hoped to settle separate claims for damages over the spill ahead of the trial, but said this month that claims by the states of Louisiana, Alabama, Mississippi and Florida of $34bn (£21.5bn) for economic and property damage under the Oil Pollution Act were “overstated”.

BP’s total liability could now come to $90bn, BP revealed at its full-year results presentation this month, more than double the amount the British company has set aside for the accident, which killed 11 men and spilled millions of barrels of oil into the Gulf.

http://www.telegraph.co.uk/finance/newsbysector/energy/9882017/BP-wins-ruling-to-cut-potential-Gulf-of-Mexico-fine-by-3.4bn.html