A US Justice Department lawyer opened the trial on Monday by accusing the London-based corporation of putting profit margins ahead of safety, something he argued, led to the disaster.

"The evidence will show that BP put profits before people, profits before safety and profits before the environment," Mike Underhill said in an opening statement. "Reckless actions were tolerated, sometimes encouraged by BP to squeeze every dollar," he added. "Every fork in the road, BP chose time and money over safety in the operation of what (one rig worker) called the 'well from hell.'"

The defense lawyer representing BP conceded that the oil giant had made mistakes, but sought to deflect much of the blame to two other companies involved. Mike Brock accused the company that owned the rig, Transocean Ltd. of failing to properly maintain something called a blowout preventer. He also pointed the finger at cement services contractor Halliburton, saying it had used a “bad slurry,” which failed to prevent oil and gas from travelling up the well.

BP said it had already spent or committed up to $37 billion (27.8 billion euros) on cleanup, restoration, payouts, settlements and fines, including more than $4 billion in penalties. In this civil case, being heard in New Orleans, it is seeking to prove that its actions did not amount to gross negligence under the US Clean Water Act.

If it fails to convince US District Judge Carl Barbier, who is hearing the case without a jury, BP could be ordered to pay tens of billions more. The other two companies involved could face a similar fate.

The judge said he planned to hear the trial in three phases, the first of which was to determine what caused the oil spill, and to what extent, if at all, the companies were to blame.

The attorney general for the state of Alabama, Luther Strange, said he would seek to prove that each of the companies had acted with "gross negligence and willful misconduct."

"We will ask the court at the end of this trial to rule that all three – BP, Transocean, and Halliburton - are liable for punitive damages to the state of Alabama," he said.

The second phase of the trial would seek to determine how much crude flowed into the Gulf of Mexico, while a third, which isn't expected to start until next year, would consider damages.

An explosion on BP's drilling platform Deepwater Horizon killed 11 workers and released millions of barrels of oil into the Gulf of Mexico on April 20, 2010. It took almost three months to contain the blowout.

As well as causing extensive environmental damage along the US gulf coast, the oil spill negatively impacted tourism and fishing industries across several states.

pfd/lw (Reuters, AFP, AP)