Media playback is unsupported on your device Media caption "The Gulf of Mexico is a more challenging drilling environment than many other parts of the world"

BP's departing boss Tony Hayward has told MPs that the Gulf of Mexico oil spill was "devastating" to him.

Mr Hayward's personal responses to the explosion, which killed 11 workers, have been criticised in the past.

On a visit to Louisiana to view the spill's damage, Mr Hayward had told reporters he "wanted his life back".

The Commons Energy Committee is questioning both Mr Hayward and BP's head of safety, Mark Bly, on the firm's attitude to safety.

Asked whether BP paid sufficient regard to safety matters, Mr Hayward told the committee that over the past three years the company had made a major investment in safety, spending $14bn (£9bn) and recruiting thousands of people.

"And it is undeniably the fact that because of all of that, this particular incident is so devastating to me personally because we have made an enormous amount of progress in that three-year period," he said.

My Hayward's demeanour was in contrast to when he faced a US Congressional committee, when he appeared crushed and evasive.

He was then pilloried for failing to answer the committee's questions.

In a veiled reference to that hearing, Tim Yeo, the chairman of the energy and climate change committee, has warned his colleagues not to use Mr Hayward's appearance for "point scoring" rather than serious inquiry.

One issue the UK committee is considering is whether UK offshore oil safety rules need to be changed as a result of the Gulf of Mexico spill.

My Hayward said no changes would be made to its £12bn ($18.5bn) investment in the North Sea energy fields.

He told the panel: "BP remains very committed to oil and gas exploration in the North Sea and intends to make absolutely sure all the lessons, in all the dimensions we have discussed today, are fully applied to everything we do in the U.K."

Meanwhile, in the US on Wednesday, the interior department said it was set to require oil companies to plug 3,500 non-producing oil wells in the Gulf of Mexico, in an effort to prevent future leaks.

The department will also require companies to dismantle 650 unused oil and gas platforms, some of which have sat idle for decades without inspection for leaks.

Administrative error

On Wednesday, the Financial Times newspaper said offshore inspection records showed BP did not comply with rules about regular training for offshore operators on how to respond to an oil spill.

Mark Bly told MPs the issue had been addressed: "It is true a handful of people - less than 10 - had not undergone all the training, which was mostly a computer-based refresher."

Mr Bly led an internal investigation by BP into the reasons for the explosion.

It found BP was responsible in part for the tragedy, but also placed some blame on rig owner Transocean and cement contractor Halliburton.

"No single factor caused the accident, and multiple parties including BP, Haliburton and Transocean were involved," he said.

Mr Hayward strongly denied cost-cutting was a factor in the Deepwater Horizon disaster, telling MPs that "safety is the first call on every dollar BP invests. Before we invest in anything, we invest in safety".

Mr Hayward will step down next month from the position of chief executive to be replaced by the man in charge of the Gulf clean-up operation, BP managing director Bob Dudley.