Two damning reports have blamed cost-cutting by BP for one of the worst onshore oil spills in Alaska in another huge blow to the UK group.

The reports, commissioned by BP after a ruptured pipeline led to the spillage of 200,000 gallons of crude at the Prudhoe Bay field last year, will place yet more pressure on Tony Hayward, the new chief executive.

He was in charge of BP’s exploration and production division before being promoted to the top job last week.

One report, by a US consulting firm, claims that deep cost cuts imposed by BP management contributed directly to a complacent attitude towards the risks of corrosion in pipelines at the Prudhoe Bay site.

The second, carried out by CC Technologies, a specialist engineering firm, attacks BP’s failure to carry out routine maintenace.

A US congressional committee is reviewing both reports as part of a continuing investigation into the spillage, which took place in March last year.

According to Reuters, a source in Congress said: “The reports speak to the fact that top-down cost-cutting was going on without any risk analysis.”

The reports come only two months after the US Chemical and Safety Board slammed BP for cost-cutting that the board claimed contributed to the Texas City refinery blast that killed 15 people in 2005.

It said: "Warning signs of a possible disaster were present for several years, but company officials did not intervene effectively to prevent it."

A congressional hearing into Prudhoe Bay is expected next Wednesday.

A BP spokesman said that the group did not plan to release copies of the findings until “we’ve had an opportunity to meet the members of the committee”.

The report by CC Technologies said that BP’s failure to flush out sediment regularly inside the Prudhoe Bay pipeline allowed corrosive bacteria that caused the rupture to thrive.

The sediment shielded bacteria from corrosive-preventing chemicals injected by BP.

BP had not used a device called a pig to clean the inside of the pipeline since 1998, a decision already criticised by federal regulators.

BP has already begun overhauling its US management structure.

Bob Malone, the new BP America chief executive, has more authority over the group’s operations.

The group announced on Tuesday that it had appointed its first independent safety expert, as recommended this year by the Baker report into the Texas City blast.

Mr Hayward took over as chief executive last week when Lord Browne of Madingley sensationally resigned after it emerged that he had lied to a court about a love affair with Jeff Chevalier, a 27-year-old former student.

On taking the job, Mr Hayward told staff that it was “time to move on, rebuild momentum and restore pride”.

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