BP said it will immediately appeal to the United States Court of Appeals as it believes the findings of the District Court for the Eastern District of Louisiana were not supported by the evidence at trial.

"The law is clear that proving gross negligence is a very high bar that was not met in this case. BP believes that an impartial view of the record does not support the erroneous conclusion reached by the District Court," it said.

"The Court has not yet ruled on the number of barrels spilled and no penalty has yet been determined. The District Court will hold additional proceedings, which are currently scheduled to begin in January 2015, to consider the application of statutory penalty factors in assessing a per-barrel Clean Water Act penalty," it said.

It added that the Clean Water Act requires the District Court to consider a number of factors in determining an appropriate penalty. The statutory maximum penalty is $1,100 per barrel where the court finds simple negligence and $4,300 per barrel where the court finds gross negligence or wilful misconduct.

(Reporting by Dmitry Zhdannikov,; Editing by Kate Holton)