The explosion at the BP-operated oil rig in April killed 11 workers and caused the worst oil spill in US history.
In an internal BP report released this afternoon, BP said 'no single factor' caused the disaster and defended the decisions that US politicians have said represented cost-saving measures that contributed to the explosion.
These measures included its much-criticised single-casing well design, its choice to use fewer centralisers when cementing the well and its decision to replace heavy drilling mud, which was keeping the well under control, with lighter water.
The report, conducted by BP's head of safety, Mark Bly, highlighted eight key failures that, in combination, led to the explosion.
Most of these factors would normally be the responsibility of either Transocean, as rig operator, or Halliburton, which cemented the well.
However, BP denied it was shifting blame and accepted that one of its representatives, in conjunction with Transocean, had incorrectly interpreted a safety test that should have flagged up risks of a blowout.
Nonetheless, the report included some stinging criticism - all directed at its contractors.
'To put it simply, there was a bad cement job,' outgoing Chief Executive Tony Hayward said in a statement.
BP said decisions made by 'multiple companies and work teams', including itself, contributed to the accident which arose from 'a complex and interlinked series of mechanical failures, human judgments, engineering design' and communication breakdowns.
The company has already rejected any suggestion that it was guilty of gross negligence over the spill that spewed an estimated 4.9m barrels of oil into the Gulf, but faces potential multi-billion-dollar lawsuits.
The leaking Macondo well has now been secured but the disaster is being examined in a string of court cases and probes, including a criminal investigation being carried out by the US Department of Justice.
BP has already spent $8bn (€6.3bn) trying to contain the disaster and has forecast that it will eventually cost the group more than $32.2bn after clean-up costs and compensation are taken into account.
US lawmakers have accused the oil giant of sacrificing safety to improve its profit margin but Mr Hayward denied this during a hostile grilling in Congress in June.
Mr Hayward subsequently announced he would quit the top job in October.
