Image caption The disaster was the worst US offshore oil spill

The US Justice Department has accused BP of "gross negligence and wilful misconduct" over the Deepwater Horizon disaster, claims which BP denies.

The allegations came in papers filed in the federal court in New Orleans.

The Deepwater Horizon rig had been leased by BP. It exploded on 20 April 2010, killing 11 workers and spilling millions of gallons of crude oil.

If the government can prove gross negligence it can triple the damages BP may have to pay to $21bn (£13bn).

The case is due to go to trial in New Orleans in January 2013, although talks are underway between BP and the US government to try to settle the claims.

"The behaviour, words, and actions of these BP executives would not be tolerated in a middling size company manufacturing dry goods for sale in a suburban mall," the government said in its 39-page filing.

BP has denied the claims. "BP believes it was not grossly negligent and looks forward to presenting evidence on this issue at trial in January," the company said in a statement.

Transocean, the Swiss-based company that owned the rig, declined to comment, the Reuters news agency said.

The legal filing said that errors made by BP and Transocean in deciphering a pressure test on the well supported the government's case.

"That such a simple, yet fundamental and safety-critical test could have been so stunningly, blindingly botched in so many ways, by so many people, demonstrates gross negligence," it said.