The rig explosion on 20 April 2010 had killed 11 workers and spilled oil into the Gulf of Mexico for nearly three months, which affected the shorelines of many states.
The U.S. District Judge Carl Barbier in New Orleans, Louisiana held a trial without a jury in 2013.
The judge ruled that BP was largely at fault and the two other companies involved in the case – Transocean and Halliburtonwere not to be blamed as much.
According to Barbier, BP should claim 67% of responsibility for the oil spill, while drilling rig owner Transocean and the US-based cement firm Halliburton should assume 30% and 3% responsibilities, respectively.
BP may be imposed with lower fines for pollution violations, but it is still likely to surpass the $1bn fine paid by Transocean, which owns the Deepwater Horizon drilling rig.
The ruling stated that there were several instances to show that BP took cost cutting measures irrespective of the safety risks.
This decision is one of the largest legal setbacks for BP in the last four years.
Even though the initial cleanup following spill has been completed, scientists are still monitoring the aftereffects of the spill in the gulf.
However, BP did not agree with the judgment, which claimed that the company was grossly negligent. It plans to appeal the ruling.
The company claimed that the judge’s finding of willful misconduct on the part of the company is not supported by the evidence at trial.
If it goes for appeal, BP may end up paying less than $18bn in fine for the pollution violations.
