A US federal judge in New Orleans is sticking to his ruling that said BP’s conduct in the 2010 Gulf of Mexico oil rig disaster amounted to “gross negligence”.

It could mean close to $US18 billion ($A19.48 billion) in federal penalties for the oil giant.

US District Judge Carl Barbier on Thursday rejected BP’s call to either amend his September 4 judgment or hold a new trial on the issue.

BP lawyers filed a motion in October arguing that Barbier’s ruling was based on expert testimony that had been excluded from the earlier trial.

Barbier disagreed in an 11-page ruling that included excerpts from the testimony. Barbier said there was no basis for BP’s claim that the testimony was unfair or prejudicial.