Cure the NHS campaigner Julie Bailey said NHS boss Sir David Nicholson had not accepted responsibility for what happened at Stafford and is simply "waiting for his retirement".
"We're disappointed that he's not going immediately to be honest", she said, "this man presided over the biggest disaster in the history of the NHS, he'll be leaving with a huge pension pot and with his knighthood intact but he'll be going eventually and then we can start to cure the NHS."
The head of the NHS has announced he is retiring next year. Sir David Nicholson was in charge of the regional health authority responsible for Stafford hospital, where hundreds of patients died needlessly between 2005-2008.
Latest NHS figures show that when he leaves next March, his pension pot will be worth nearly £1.9 million.
Although it is dated May 21, one paragraph says: "In getting ourselves ready for the 1 April 2013 we should..." which implies that the letter was drafted before April 1 - the day that the controversial NHS reforms were implemented.
Sir David goes on to say that he has stayed in the role to oversee NHS reforms come into place.
He thanks NHS England's chair Professor Sir Malcolm Grant for support and understanding "with regard to the complexity of my role".
Professor Grant replied: "Thank you for your letter conveying your intention to retire as CEO of NHS England. I was sorry but not surprised to have it.
"Your career within the NHS over 35 years has been exceptional, and your leadership through the radical changes of the past two years has been fundamental to their success."
Commenting on the announcement by NHS boss Sir David Nicholson that he will retire next year, Chief executive of the NHS Confederation Mike Farrar said:
"Despite the difficulties of recent months, today's announcement provides an opportunity to focus on Sir David's contribution to the NHS over the past three decades, the significant achievements over the lifetime of his career and during his time as the chief executive of the NHS.
"Sir David came into office as NHS chief executive in 2006 and immediately led a major recovery from the deficit that the health service faced at that time.
"Over subsequent years he led the delivery of a remarkable reduction in waiting times for urgent and elective care, with access to treatment improving faster than almost any comparable health system.
"There have been significant improvements in patient outcomes and a huge reduction in healthcare acquired infections. In recent years, he presided over the largest structural reform in the history of the NHS."
The Health Secretary, Jeremy Hunt, has today released a statement following the resignation of NHS boss, Sir David Nicholson.
Under Sir David Nicholson's leadership, NHS waiting times have fallen, infection rates reduced, and mixed sex accommodation is at an all-time low.
His job has often been incredibly complex and very difficult, and yet he has always had a reputation for staying calm and maintaining a relentless focus on what makes a difference on the NHS frontline.
I am also grateful to him for overseeing the successful setting up of NHS England and giving us an orderly period in which to select his successor.
Sir David Nicholson has written a letter outlining his intention to retire in March next year to the chair of NHS England Professor Malcolm Grant. In it he writes:
Whilst I believe we have made significant progress together under my leadership, recent events continue to show that on occasion the NHS can still sometimes fail patients, their families and carers. This continues to be a matter of profound regret to me but please know that on a daily basis I continue, and will always continue, to be inspired and moved by the passion that those who work in the NHS continue to show.