Under-fire NHS boss Sir David Nicholson has said he is "absolutely determined" to lead the NHS through the coming health reforms despite calls for him to resign.

Sir David said the NHS is currently at "maximum risk" as the controversial changes are implemented throughout the country. The NHS chief executive said he would stay in his role to see the reforms through.

Campaigners called for Sir David's resignation following the publication of the Francis Report into serious failings at Mid Staffordshire NHS Foundation Trust.

The health boss was in charge of the regional health authority for part of the time that patients were being mistreated at Stafford Hospital where hundreds of patients may have died needlessly after they were "routinely neglected".

"At the moment the NHS is facing its greatest challenge," Sir David told the Health Select Committee.

"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. We'll completely change the way in which we allocate resources and incentivise the NHS.

"At the same time, we have already lost 13,500 administrative and management staff that have all that corporate memory in them. So 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 both the Government and the NHS that I would see that through and I am absolutely determined to do that over the next period."

Sir David told the committee that the need to motivate NHS staff had been "lost" at the time of the Mid-Staffordshire problems, as the system focused on management systems.

"The first thing - and you can see it absolutely played out in Mid-Staffordshire and you can see it in parts of the NHS where there is poor care - (is that) motivated, supported staff provide great outcomes for patients," he said. "That connection seems to have been lost in a whole set of discussions about systems and processes."