A presidential commission has concluded that a series of poor decisions led to the technical problems that ultimately contributed to a deadly explosion and America's worst-ever oil spill. And it could happen again.

According to an excerpt released ahead of the final report by the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, there are systemic problems in the offshore oil and gas industry, as well as the government regulators that oversee it.

"Better management by BP, Halliburton and Transocean would almost certainly have prevented the blow-out," the commission concludes in the excerpt published on its website.

"The blowout was not the product of a series of aberrational decisions made by a rogue industry or government officials that could not have been anticipated or expected to occur again. Rather, the root causes are systemic, and absent significant reform in both industry practices and government policies, might well recur."

The panel also concludes that the three companies involved with the Deepwater Horizon rig and the Macondo well that exploded on April 20, killing 11 people, each made decisions that saved time or money at the expense of safety.

"Whether purposeful or not, many of the decisions that BP, Halliburton, and Transocean made that increased the risk of the Macondo blowout clearly saved those companies significant time (and money)," the panel wrote.

"BP 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," the report continues, noting that government inspectors and analysts weren't up to the task either.

Despite the report's scathing conclusions, The Oil and the Glory author Stephen Levine says it is absent one crucial word: negligence.

"If BP is found to be negligent or grossly negligent its bill for the cleanup would quadruple from $20 billion to an estimated $80 billion dollars," Levine told CTV's Canada AM in an interview from Washington early Thursday.

"Since that word was not in the report's 48 pages, there was a sigh of relief," he added. "You can see it in the markets."

BP shares were up slightly more than 2 per cent in mid-morning trading on the London Stock Exchange Thursday, but Levine says the quick reaction may be misguided.

"The market is seeing reason for assurance in the report, I'm not sure it should see that," he said.

While the markets react, the three companies involved have resumed their finger-pointing.

In its response, BP PLC said the presidential panel's suggestion that the explosion and spill were caused by a combination of factors involving more than one company echoed its own findings released in September.

"Today's release largely adopts the preliminary findings of the commission's chief counsel, and like several other inquiries, including BP's internal investigation, concludes that the accident was the result of multiple causes, involving multiple companies," BP said in a statement.

In its response, the owner of the Deepwater Horizon rig Transocean Ltd. said, "the procedures being conducted in the final hours were crafted and directed by BP engineers and approved in advance by federal regulators."

Contractor Halliburton Co., said it acted at the direction of BP and was "fully indemnified by BP."

In addition to BP's probe, the U.S. Congress has already concluded its own inquiry into the Gulf of Mexico disaster.

The presidential commission's complete report is due Jan. 11. In the meantime, the Justice Department and a joint U.S. Coast Guard-Bureau of Ocean Energy Management, Regulation and Enforcement panel are continuing their own investigations.