Five former health secretaries will tomorrow give their unequivocal backing to David Nicholson, the beleaguered head of the NHS who faces calls for his resignation in the wake of the Mid Staffordshire scandal, in interviews with The Independent.

Sir David will give evidence to Parliament tomorrow morning about what he knew about the events at Stafford Hospital, where hundreds of patients died as a result of appalling derelictions of care between 2005 and 2009.

But ahead of the hearing, the five former ministers from both Conservative and Labour governments back him, and criticise the virulent campaign against him. They warn that at a time when the NHS has to make savings of £20bn, it was vital he remained in post to ensure stability.

"I have been appalled by the campaign against David Nicholson and I think it is grossly unfair," the former Labour health secretary, Patricia Hewitt, told The Independent. "If you have lost a family member in such distressing circumstances of course you are going to look for someone at the top of the organisation to be held responsible.

"But the Francis report makes clear Stafford happened because of a shocking lack of clinical and managerial governance for which the board of the hospital was responsible. David Nicholson is not."

Alan Milburn, who never worked directly with Sir David at the Department of Health, also sprung to his defence. He suggested it was easier for parts of the media to scapegoat hospital managers than the doctors and nurses who had been directly responsible for neglecting patients.

"The much reviled managers are in the line of fire but I am afraid if you read the report carefully it is the much-lauded nurses and doctors who were equally to blame," he said. "The easiest thing is to always look for the knee-jerk response, put a head on a platter and then everything is solved. But it isn't, is it?"

Alan Johnson, another Labour health secretary, said there was "never any doubt" in his mind that Sir David "was part of the solution to raising quality in the NHS rather than the problem", while Andy Burnham, the current shadow Health Secretary, also backed him.

The former Conservative health secretary, Andrew Lansley, made clear he supports Sir David: "David Nicholson's knowledge of, and commitment to, the NHS means he should be given the opportunity to take the NHS through the cultural and structural changes it so badly needs."

But the Conservative MP Sarah Wollaston, a former GP and member of the Health Select Committee, said she believed that Sir David should step down because he oversaw a target-driven regime that ignored patient concerns: "People say he should stay to ensure a smooth transition to the new system. But that suggests that we should keep the system as it is."