BP has handed the bill for clearing up the disastrous 2010 Deepwater Horizon oil spill to Halliburton, the US contractor it claims botched the cement work on the failed rig.
The oil group has filed a suit in New Orleans seeking "the amount of costs and expenses incurred by BP to clean up and remediate the oil spill, the lost profits from and/or diminution in value of the Macondo prospect, and all other costs and damages incurred by BP related to the Deepwater Horizon incident and resulting oil spill", according to the filing.
BP did not specify the amount of damages it is seeking from Halliburton, which provided cement contracting services on the well in the Gulf of Mexico. But it previously estimated the clean-up will cost $42bn (£27bn). It has spent $14bn in the Gulf coast region cleaning up the spill with another $20bn set aside for economic claims and restoration work.
The oil firm wants Halliburton to pay damages "equal to, or in the alternative proportional to Halliburton's fault," to cover clean-up costs and any government fines BP may face.
A Halliburton spokeswoman said: "Halliburton stands firm that we are indemnified by BP against losses resulting from the Macondo incident."
This is the latest salvo in a continuing battle between the former partners. Halliburton had asked a court to force BP to recognise a contractual agreement protecting it against possible clean-up costs. Last month BP accused Halliburton of destroying evidence related to the explosion at Deepwater Horizon that led to 11 deaths and the worst oil spill in US history.
BP alleged Halliburton had destroyed evidence on cement testing and violated court orders by not producing "inexplicably missing" computer modelling results. Halliburton said BP had known about these post-incident tests for some time and had "chosen this late date in the litigation to mischaracterise the results of such tests".
The Deepwater disaster led to more than 200m gallons of oil being released into the Gulf and has sparked a series of lawsuits and federal investigations into the companies involved.
Last month BP reached a $250m settlement with Cameron International, the designer and manufacturer of the rig's failed blowout preventer, ending all claims between the two relating to the spillage. The oil firm has also reached agreements with other companies involved in the rig including Anadarko and Weatherford. But agreements with Halliburton and Transocean, which operated the rig, have proved harder to achieve, with both parties launching lawsuits of their own.
At the time of the Cameron settlement BP chief executive Bob Dudley hit out at his former partners, accusing them of "refusing to accept responsibility for their roles in the accident and for contributing to restoration efforts".
Last year Transocean issued a 854-page report on the Deepwater disaster that largely blamed BP for "a succession of interrelated well design, construction and temporary abandonment decisions that compromised the integrity of the well and compounded the risk of failure".
The ongoing legal battles come as the US justice department is believed to be preparing possible criminal charges against BP engineers. According to US reports, the government could bring charges against the oil firm early this year.
The justice department has been investigating the fatal disaster since 2010 and set up a Deepwater Horizon taskforce to assess whether criminal charges could be brought against the well's operators. It is believed to be assessing whether false information was given to regulators about the risks of drilling at the Macondo site.
In December BP was accused of five new violations of safety and environmental laws by the bureau of safety and environmental enforcement, the regulator investigating the Deepwater disaster.
The bureau accused BP of violating a rule requiring the company to conduct an accurate pressure integrity test in the well. It also alleged BP had failed to suspend drilling operations when work slipped outside the safe drilling margin agreed in its government-approved permit to drill. BP has challenged the bureau's finding.
The alleged violations follow an earlier report that issued 15 citations against BP, Halliburton and Transocean.