According to the draft report from the US Chemical Safety Board, the blast was the result of lax safety culture at BP.
The report also said that the agency in charge of spotting safety problems had failed to see warning signs.
BP's Texas City plant south of Houston was hit by a fatal explosion in 2005, which also injured 180 people.
The UK oil company said on Tuesday that it disagreed strongly with parts of the report.
According to the draft report, a number of factors contributed to the explosion including cost-cutting, worker fatigue, and a failure by the whole of BP's management to address safety issues.
Carolyn Merritt, chairman of the Chemical Safety Board (CSB), has said that the board had been "absolutely terrified" by the poor safety culture at the refinery.
On Tuesday, she added that programmes designed to protect staff and the public "deserve the same level of attention, investment, and scrutiny as companies now dedicate to maintaining their financial controls".
"The combination of cost-cutting, production pressures and failure to invest caused a progressive deterioration of safety at the refinery," Ms Merritt said.
The CSB also singled out the US federal work safety watchdog, the Occupational Safety and Health Administration, for criticism.
"Rules already on the books would likely have prevented the tragedy in Texas City," Ms Merritt said.
"But if a company is not following those rules, it is ultimately the responsibility of the federal government to enforce good safety practices before more lives are lost."
Ms Merritt told Radio 4's The World Tonight that investigators had begun to suspect much wider safety problems at BP soon after starting their inquiry in 2005.
Last month, BP said that while the report would find "shortcomings" in the performance of some of its managers, there was "no evidence that anyone acted in bad faith or violated BP's code of conduct".
BP's own earlier report into the blast, led by former US Secretary of State James Baker, found that BP had focused on personal safety at the expense of broader safety processes.
The Baker report said similar problems existed at all five of BP's US refineries.
BP said that it was putting in place all the recommendations of the Baker report, adding that it had taken "significant steps" to improve safety at its US refineries.
"BP is committed to preventing such a tragedy from occurring again," the company said.
The US Justice Department is currently investigating whether BP was criminally responsible for the blast.
The CSB is scheduled to vote on the report at a public meeting on Tuesday.
- 184 Labor