A key federal report is blaming British Petroleum and its partners for last year's Gulf of Mexico oil spill, the worst offshore spill in U.S. history.

The U.S. Coast Guard and Bureau of Ocean Energy Management, Regulation and Enforcement report says the disaster was the result of poor management, a faulty cement job, and other missteps. Details of the report were released Wednesday.

The Deepwater Horizon oil rig explosion in April 2010 killed 11 people and set off an 85-day underwater leak that spewed nearly 5 million barrels of oil into the Gulf of Mexico.

Earlier reports put blame for the blowout of the Macondo well on BP; Halliburton, the company responsible for cementing the well; and Transocean, the owner of the oil rig.

The presidential commission report, released earlier this year, said the deadly explosion and massive spill could have been avoided.

The report said BP, Halliburton, and Transocean cut costs and took shortcuts, which increased the risk of a blowout. It specifically singled out a flawed design of the cement used to seal the well.

Lawsuits, investigations, and changes in industry regulation have since resulted. The newest report is expected to lead to further legal ramifications for BP and its partners.