BP told “outright lies” as it tried to hide the amount of oil that was spilling into the Gulf of Mexico following the Deepwater Horizon oil rig disaster, a court heard on Monday, in a new phase of the trial that could ultimately determine how much the company will pay in fines. In opening statements of the latest phase of the trial over the fatal 2010 disaster, plaintiffs’ attorney Brian Barr said BP failed to prepare for a blowout and compounded the problem by lying about how much oil was flowing from the well. He said BP was woefully unprepared for the disaster. “BP’s plan was nothing more than a plan to plan,” said Barr, according to the Guardian newspaper. US district judge Carl Barbier in New Orleans, who is presiding over the trial, is already weighing whether BP’s actions ahead of the disaster and during the subsequent spill reached the level of “gross negligence”. The second phase of the trial, expected to last 14 days, will cover the size of the spill and BP’s efforts to contain it. The Department of Justice said the claims 4.2m barrels poured from Deepwater Horizon after the fatal fire and explosion that claimed 11 lives. BP estimates the figure was closer to 2.4m barrels. The figures will determine the ultimate size of BP’s fine, which could be as high as $18bn.