BP's monitoring IT systems on the failed Deepwater Horizon oil rig relied too heavily on engineers following complex data for long periods of time, instead of providing automatic warning alerts.
That is a key verdict of the Oil Spill Commission, the authority tasked by US President Barack Obama to investigate the Gulf of Mexico disaster. It also criticised decisions to ignore cement modeling tests, as well as other cementing and management strategies.
Three weeks ago, the US government launched a $21.1 billion (£13.5 billion) lawsuit against BP and its drilling partners, alleging that they had "failed ... to use the best available and safest drilling technology" to monitor pressure in the well.
The explosion on the rig, last April, resulted as huge pressure of dangerous hydrocarbons built up in the well. Eleven people died in the accident, and over the following months millions of barrels of oil spewed into the sea until the well was eventually capped.
The OSC said in a chapter released today that the monitoring systems on the rig before the explosion did provide the necessary safety data, including about pressure in the well.
However the systems relied on too much on engineers' astute manual observation of data flows. It also noted that the systems used by BP were standard in the energy industry.
When engineers were tasked with so many simultaneous functions over long work days, they needed much more support from systems. The standard industry ones used by BP were too basic, the OSC noted.
In a chapter of their report, the committee members expressed exasperation that while the industry was regularly conducting highly complex drills in order to satisfy the global demand for oil, IT systems simply have not kept pace with the complications and risks of deepwater drilling.
"In the future, the instrumentation and displays used for well monitoring must be improved," said the OSC. "There is no apparent reason why more sophisticated, automated alarms and algorithms cannot be built into the display system to alert the driller and mud logger when anomalies arise."
The OSC said there was no excuse for drilling companies to be relying on engineers to spot small changes in data - which could lead to severe consequences - when the individuals "sit for 12 hours at a time in front of these displays".
BP used the Halliburton Sperry Sun system and the HiTec system from rig owner Transocean for monitoring and these had provided the right data to demonstrate a "kick" or dangerous rise in pressure was occurring.
But the OSC insisted it was "no longer acceptable" for oil companies to rely on a system that "requires the right person to be looking at the right data at the right time, and then to understand its significance in spite of simultaneous activities and other monitoring responsibilities".
The management style was also criticised, as engineers worked long days handling complex data and technology. In recent weeks, a key engineer on the rig said in testimony that he had stepped away from his safety monitor for a brief cigarette break, and that at this moment he missed the complex warning signs on screen.
The OSC also reiterated its concerns that BP had ignored the results of the Halliburton OptiCem cement modeling software, which had stated that more stabilisers - called centralisers - were needed to support the underwater cement work. It had done so in order to save time, it noted.
But Halliburton, the cement contractor, was also criticised for possibly failing to share data with BP from tests on its cement slurry mix. Its early tests may have shown the mix was not stable, the OSC said, yet it had still continued the cement job.
Meanwhile, investigations have still not uncovered what happened to the blowout preventer, which sits on the well head and is intended to prevent this type of accident. Forensic examinations on the device are continuing. The OSC suggested a lack of proper maintenance of those automated and manual safety devices may be at fault.
BP said in a statement that it "supports" the findings of the report, which it said "concludes that the accident was the result of multiple causes, involving multiple companies". It has introduced a new safety division directly reporting to chief executive Bob Dudley, it said.
A spokesperson at Halliburton said its own tests were "complete prior to pumping the cement job", adding that the company "acted at the direction of BP", which it said had placed "restraints" on the cement design. Transocean had not commented at the time of writing.
The full report will be published next week.