LONDON (REUTERS) - The British government has urged the US Supreme Court to review an appeals court ruling against BP Plc over a 2010 Gulf of Mexico oil spill that produced one of the largest class actions in American history.

A Louisiana court ruled last week that BP was "grossly negligent" and "reckless" in the spill, a move that could add nearly US$18 billion (S$22.6 billion) in fines to more than US$42 billion in charges.

In a friend of court brief, the UK government said the ruling by US District Judge Carl Barbier raises grave international concerns by undermining confidence in the "vigorous and fair resolution of disputes."

The filing said BP, which has "gone to great lengths to restore the Gulf Coast", was now being required to pay large sums to others who were not injured by the Deepwater Horizon oil spill.

The British government said treatment meted out to BP undermined the fairness and trust necessary for international commerce.

The United States and Britain conduct more than US$200 billion in trade each year, and UK businesses are responsible for 17 per cent of all foreign direct investment in the United States, according to the filing.

BP last week said it would appeal the court's ruling. In response to the brief, BP said the petition emphasizes the importance of fair and consistent application of law. BP argued that the Fifth Circuit's decisions, if allowed to stand, will fundamentally alter class action law and discourage companies from settling complex cases.

"..if companies are exposed to liability for losses they did not cause, likely discourage them from investing in the United States," BP said in a statement.