On the first anniversary of the explosion that triggered the giant Gulf of Mexico oil spill, the well operator BP has gone to court to force two other companies to share the blame — and the costs.

On Wednesday, BP sued Cameron, the maker of the blowout preventer that failed, and in a separate case cited faults by Transocean, owner of the Deepwater Horizon drilling rig that caught fire and sank. BP is seeking payments to help cover the environmental fines and damage payments that are expected to run up to $40 billion.

The London-based oil giant has asserted in court that “negligence” on the part of Cameron and Transocean caused the accident that killed 11 men and caused widespread environmental damage. BP said that Cameron’s “faulty design” of the blowout preventer was one key reason for the disaster.

BP cited a recent federal investigation that found that the blowout preventer, which rested on the sea floor, was unable to fully close and secure the well, in part because the drill pipe was not centered in the place where the blind shear ram — the most powerful of the blowout preventer’s devices — was supposed to cut and seal the pipe.

Cameron issued a statement noting that Wednesday was the deadline for the companies to file claims against one another, and that “in order to protect ourselves, we, too, have filed” claims against other companies involved in the accident.

Although on the day of the accident, senior BP managers were visiting the Deepwater Horizon to congratulate its crew on the rig’s safety record, in a court filing Wednesday BP gave a litany of 17 errors and failings on the part of Transocean. They included items such as “failing to properly inspect” the rig, “failing to properly operate” it, “negligently hiring” personnel, and “failing to react to danger signs.”

“But for Transocean’s improper conduct, errors, omissions, and violations of maritime law, there would not have been any blowout of the exploratory well,” BP said.

A Transocean spokesman, Lou Colasuonno, issued a statement calling BP’s allegations ”specious and unconscionable.” It said that the Deepwater Horizon “was a world-class drilling rig manned by a top-flight crew that was put in jeopardy by BP, the operator of the Macondo well, through a series of cost-saving decisions that increased risk — in some cases severely.”

The Transocean statement added that “BP set the stage for this disaster,” and called the oil company’s assertions “the latest desperate bid by BP to turn its back on” an agreement with Transocean to “assume full responsibility” for the costs of pollution and environmental damage caused by the spill.