A “terrifying safety culture” at BP was behind an explosion at a Texas oil refinery that killed 15 people and injured 180 others, the head of an official inquiry of the incident said today.

Carolyn Merritt, chairman of the US Chemical Safety Board (CSB), said: “As the investigation unfolded, we were absolutely terrified that such a culture could exist at BP.”

The CSB will unveil its final report into the explosion tomorrow after an investigation lasting two years. BP has already settled several lawsuits relating to the explosion.

A BP spokesman said: “Our own internal report found serious problems with the safety culture at Texas City and also identified the critical factors leading to the terrible tragedy that occurred there.”

He added: “We are addressing the safety culture issues across BP, as we have been doing since the accident in 2005.”

An advisory panel convened by BP and led by James Baker, the former US Secretary of State, found dangerous conditions at all five of BP’s US refineries and recommended an overhaul to safety procedures across the US refining sector.

The CSB’s final report will follow a series of separate investigations that have produced heavy criticism of BP’s safety regime at Texas City and in the US generally. The company was fined $21 million in September 2005 by the Occupational Safety and Health Administration (Osha) for 301 violations, the largest fine in the history of the US regulator.

BP suffered a greater blow in January when the Baker panel accused BP of ineffective leadership and of tolerating an undisciplined safety culture and having a complacency towards risk.

The panel said BP had been obsessed with personal accident statistics, the catalogue of trips, falls and road accidents, while failing to focus on the safety of core industrial processes within its US refineries. The panel concluded that BP had failed to ensure that adequate resources were committed to process safety but individual members of the panel said that they found no evidence of deliberate cuts to safety funding.

That conclusion contrasted with previous statements made by Ms Merritt, who, in October last year, accused BP of adopting a “cheque book” mentality towards safety when she presented the organisation’s preliminary findings.

Then, the CSB said BP had allowed the continued use of unsafe and antiquated equipment and of tolerating maintenance deficiencies. In her October presentation, she said: “Every successful corporation must contain its costs. But at an ageing facility like Texas City, it is not responsible to cut budgets related to safety and maintenance without thoroughly examining the impact on the risk of a catastrophic accident.”

The Texas City fire occurred when refinery staff overfilled an isomerisation unit, a device that refines low octane to high octane fuel. The overflow of liquid was discharged into the blowdown stack, a chimney intended to vent vapours into the atmosphere but the stack could not cope with the volume and a cloud of flammable hydrocarbons was expelled, fell to the ground and ignited.

The company has been swamped by a torrent of civil litigation from victims of the fire and has set aside $1.6 billion for claims of which 1,000 have so far been settled.

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