The US Supreme Court has refused to hear an appeal by oil and gas giant BP and its partner Anadarko Petroleum, which seeks to avoid penalties for the massive 2010 Golf of Mexico oil spill.
The two firms argued the oil did not leak from the well itself, but from a broken underwater pipe at the Deepwater Horizon drilling rig, which was operated by another company.
The two firms were appealing the decision last year made by a lower court under a US federal pollution law.
The original ruling by the New Orleans-based 5th US Circuit Court of Appeals said the companies were liable for civil penalties under the federal Clean Water Act.
BP and Andarko claimed drilling contractor Transocean, who owned the destroyed Deepwater Horizon rig, should be the one to pay any fines for the environmental disaster, which directly affected 180,000 square kilometres of ocean.
The Deepwater Horizon drilling rig exploded on 20 April 2010, killing 11 rig workers. Following the explosion, 172 million gallons of oil spilled into the Gulf of Mexico as the firms struggled for weeks to contain the leaks.
The oil spill is considered the largest offshore environmental disaster in US history.
BP could face a maximum penalty of $13.7bn under the Clean Water Act. Anadarko, who owned 25 per cent of the damaged rig says it could be required to pay more than $1bn.
US District Judge Carl Barbier in New Orleans has not yet imposed penalties, but has ruled that BP was grossly negligent.
Overall, BP has incurred more than $42bn in costs for the spill, including clean-up, fines and victim compensation.
The rig operator Transocean agreed last year to pay the US government $1bn in civil penalties over the spill.