BP says no single factor caused the oil spill in the Gulf of Mexico, the worst ecological catastrophe in recent US history.
Instead, "a sequence of failures involving a number of
different parties" led to the explosion which killed 11 people and
caused the leak.
The company said it had accepted all the recommendations in the report, and would implement them worldwide.
An estimated 4.9m barrels of oil leaked into the Gulf after the blast.
The well as capped on 15 July, and an operation to permanently seal it is due to take place in the next few weeks.
In the 193-page report,
BP said that decisions made by "multiple companies and work teams"
contributed to the accident, which it said arose from "a complex and
interlinked series of mechanical failures, human judgments, engineering
design, operational implementation and team interfaces".
It said that "over a 40-minute period, the Transocean rig
crew failed to recognise and act on the influx of hydrocarbons into the
well" which eventually caused the explosion.
The report, published on the company's website, criticised
the cementing of the well and repeated previous criticism of the blowout
BP and Transocean staff incorrectly interpreted a safety test which should have flagged up risks of a blowout.
"To put it simply, there was a bad cement job and a failure
of the shoe track barrier at the bottom of the well, which let
hydrocarbons from the reservoir into the production casing," said
outgoing chief executive Tony Hayward.
"The negative pressure test was accepted when it should not
have been, there were failures in well control procedures and in the
blow-out preventer; and the rig's fire and gas system did not prevent
ignition," he said.
The blowout preventer that failed was
recovered from the Gulf of Mexico on Saturday and transported to a Nasa
facility near New Orleans where it will be placed in the custody of the
US Justice Department and examined.
BP's incoming chief executive Bob Dudley said the report
proved that the explosion was "a shared responsibility among many
"We are determined to learn the lessons for the future and we
will be undertaking a broad-scale review to further improve the safety
of our operations... to ensure that a tragedy like this can never happen
again," he said in a statement.
BP says dealing with the aftermath of the spill has cost $8bn
(£5.2bn), and it has already paid out about $399m in claims to people
affected by the spill.
A national commission is expected to submit a report to
President Barack Obama by mid-January next year. A Congressional joint
investigation will submit a report later than month.
The US Justice Department is also investigating the disaster,
but its investigations will only conclude when lawyers and
investigators have found evidence, or not, of criminal wrongdoing.