The partner of Gillian Astbury, who died after slipping into a diabetic coma at the scandal-hit Stafford Hospital in 2007, told ITV News the criminal investigation into her death "has been a long-time coming".
Ron Street said what happened at the hospital was due to "several years of complacent mismanagement":
Campaign group Cure the NHS has commented on the news that the Health and Safety Executive has launched a criminal investigation into the death of a woman at scandal-hit Stafford Hospital.
Cure the NHS welcomes the announcement of a formalinvestigation into the tragic death of Gillian Astbury but we note that it hastaken six years for this to happen.
Gillian's death after nurses failed to ensure shehad vital insulin medication serves as a tragic reminder of the appalling caremany patients and their families were forced to endure...
To this day many members of Cure the NHS are saddened at the failures of the wider system to act in the interests of patients. The West Midlands SHA took no action on Ms Astbury's death between 2007 and 2010 and her incident was one of thousands left open and not properly investigated.
"Ms Astbury's death was reported as a serious untoward incident at the time and a full investigation into her care and treatment was carried out. The recommendations from that investigation were implemented.
"Actions included raising staff awareness about the care of diabetic patients and improving the information and system for nurse handovers."
Ms Hendry added: "In 2010 we reviewed Ms Astbury's dreadful care and, as a result, disciplinary action was taken."We will, of course, co-operate fully with the Health and Safety Executive's investigation."
An Health and Safety Executive (HSE) spokesman said:
Following legal advice, HSE deferred a decision to pursue the investigation into Gillian Astbury's death until the conclusion of the public inquiry, chaired by Robert Francis QC, into Mid Staffordshire NHS Foundation Trust.
We can now confirm that our inspectors have today formally started an investigation.
Our focus will be on establishing whether there is evidence of the employer (the Trust) or individuals failing to comply with their responsibilities under the Health and Safety at Work Act.
The report by Mr Francis highlighted "appalling and unnecessary suffering of hundreds of people" at the Trust between 2005 and 2009.
As many as 1,200 patients may have died needlessly after they were "routinely neglected" at the hospital.
Many were left lying in their own urine and excrement for days, forced to drink water from vases or given the wrong medication.