Cost-cutting and time-saving by BP was partly to blame for the avoidable oil disaster in the Gulf of Mexico, the the White House oil commission has concluded.
In the final chapter of its report, which will be published next week, the commission warns that the disaster is "likely to recur" because of industry complacency.
The oil spill last April was one of the worst in history, killing 11 people and many of the decisions taken by the companies involved "increased the risk of the Macondo blowout and clearly saved those companies significant time (and money)," the report found.
BP's own investigation found the accident was the result of multiple causes, involving multiple companies.
Transocean, which owned the Deepwater Horizon drilling rig, said that "the procedures being conducted in the final hours were crafted and directed by BP engineers and approved in advance by federal regulators".
The report found that BP, which owned the Macondo well, "did not have adequate controls in place to ensure that key decisions in the months leading up to the blow-out were safe or sound from an engineering perspective."
"This disaster likely would not have happened had the companies involved been guided by an unrelenting commitment to safety first," commission co-chairman Bob Graham, said in a statement. "And it likely would not have happened if the responsible governmental regulators had the capacity and will to demand world-class safety standards."
BP, Transocean and Halliburton, the companies involved, could be liable for billions in compensation to Gulf residents, as well as people who have lost money because of the oil spill, and for damage to natural resources.
BP said in a statement that it was working with government regulators to ensure that the experience in the Gulf led to improved practices.
Transocean stated that "the procedures being conducted in the final hours were crafted and directed by BP engineers and approved in advance by federal regulators."
Halliburton, which has previously criticised commission lab tests finding a faulty cement seal, said the commission had made use of selective information.
On 11 January, the seven-member commission will publish its full report into the causes of the blow-out, which spewed 4.9 million barrels of oil into the Gulf.