Sir David Nicholson has defended himself before MPs and said he is “determined” to remain in post as the NHS reforms are implemented.

The NHS chief executive appeared before the Commons health committee on Tuesday.

He was questioned intensely over his actions when he was chief executive of two West Midlands strategic health authorities overseeing Mid Staffordshire Trust - later foundation trust - and about the culture of the NHS.

His appearance follows persistent calls for him to lose his job, from campaigners, newspapers and health professionals, since the report of the Mid Staffordshire Foundation Trust public inquiry.

Sir David, while accepting there had been failures in the NHS in the past which led to a lack of focus on patients, said: “I absolutely get the changes that [now] need to happen.

“Given my commitment to the [NHS] constitution, my commitment to patients, and transparency, I think I’m the right person to take it [the changes] forward.”

Since the Mid Staffordshire scandal, Sir David said he had “redoubled” his efforts to improve quality of services in the NHS.

He highlighted the risk to the service in coming weeks as the NHS makes the transition to a new commissioning system, under the government’s reforms. Primary care trusts and strategic health authorities will be abolished at the end of this month, while clinical commissioning groups and the NHS Commissioning Board, of which Sir David is chief executive, will take on its full powers.

Sir David, appearing to highlight this situation to justify the necessity of him staying in post, said the changes were “fraught with risk”.

He said: “In the next few days we will abolish over 160 organisations and we will set up another 211 local organisations and a whole myriad of national ones. It is at maximum risk over the next few days.

“I said two years ago that I would take the responsibility of leading the NHS through this enormously complex set of changes. I promised I would see that through and I’m absolutely determined to do that.”

Sir David also told the committee he did not come across hospital standardised mortality ratios during his time in the West Midlands and that they were “not freely available” to SHAs or the NHS during that period.

Sir Brian Jarman, the GP and academic who led the development of the ratios, subsequently pointed out that Dr Foster first published the figures in its Hospital Guide in 2001, and that the information was available to SHAs online from 2004.

The commissioning board last week backed Sir David as its chief executive. Chair Malcolm Grant said the board had decided “he is the person whose command of the detail of the NHS and commitment to its future we believe to be fundamental to the success of the board”.