Her comments came after a Sky News investigation uncovered a culture of secrecy surrounding incompetent paramedics.
Relatives of patients who die are not routinely informed about disciplinary procedures by ambulance trusts or the paramedics' regulator the
Health Professions Council (HPC).
Marion Giles, 64, from Warkworth in Northumberland, was not told that her husband Grahame’s death in 2008 followed a catalogue of failures by a paramedic from the North East Ambulance Service.
The HPC heard that three junior doctors and two nurses at Wansbeck Hospital in Ashington thought Mr Giles "could have survived" a heart attack if he had been given the correct treatment.
Mrs Giles only learned the truth after Sky News found clues to her husband's identity buried in a heavily-redacted transcript of an HPC misconduct hearing.
In line with its standard practice, the regulator had not publicised the hearing locally, Mr Giles' name had not been mentioned, and his wife had not been invited.
With proper treatment, Mr Giles might have survived a heart attack
"It's criminal really, that all this went on, hidden, and they didn’t have the guts to tell me and to be honest about what had happened," she said.
"It's left me horrified to think that I’d put my trust in medical staff and now it’s made me feel they've let me down, they haven't told me the truth and it's very hurtful."
Solicitor Mary-Ann Charles, from Shaw and Company in Newcastle, says the secrecy is preventing victims' families from seeking justice and compensation.
"It sounds like a cover-up, it smells like a cover-up, and it really is acutely concerning that people can't find out what’s going on, especially when it could be of such significance to them," she said.
Peter Walsh, a campaigner for greater transparency in the NHS and chief executive of the charity
Action against Medical Accidents, said Sky's findings demonstrate a "staggering" lack of ethics.
"Action should be taken to ensure that any NHS body that is complicit with this unacceptable behaviour is held to account," he said.
Sky News studied documents from a handful of the 95 HPC misconduct hearings since 2005 that led to paramedics being struck off.
In the case of Grahame Giles, paramedic Brian Jewers had refused to follow a doctor's telephone instruction to administer a potentially life-saving drug and failed to carry out two other vital procedures.
It sounds like a cover-up, it smells like a cover-up, and it really is acutely concerning that people can't find out what’s going on, especially when it could be of such significance to them.
Mary-Ann Charles, solicitor from Shaw and Company in Newcastle Wansbeck Hospital, which raised the alarm, told Sky News it assumed the ambulance service would inform his family.
The North East Ambulance Service has not responded to requests for an explanation about why Mrs Giles was not told.
At his home in Shilbottle, Northumberland, Jewers declined to answer questions, saying: "That was three years ago, I've forgotten about it."
Earlier this year, the North East Ambulance Service paid £40,000 in compensation to James and Kerry-Ann Hopper after failing to tell them that Jewers had given "incompetent" treatment to their mother.
Their solicitor Mary Ann Charles had discovered by chance that Jewers was disciplined over the death of 40-year-old Denise Hopper in 2007.
In another case, the truth was deliberately withheld from an elderly man in Greenock, near Glasgow, whose wife had died in 2006 following misconduct by two paramedics.
The truth was withheld from one elderly widower in Scotland
A general manager for the Scottish Ambulance Service told the HPC that he "didn't really see any benefit to us" in telling the unidentified man the truth.
The manager said that, if the man was told, he could have concluded that his 72-year-old wife "might still have been here if someone else had come and done a different job.
"He is more comfortable thinking that everything that could have been done was done," he said.
The HPC panel member replied: "OK, thank you very much. I have no further questions."
A spokesman for the Scottish Ambulance Service could not say if the man had subsequently been informed and could not locate the trust's policy on contacting the relatives of negligence victims.
The London Ambulance Service did not inform the family of a man who died in New Malden in 2007 that a paramedic was being disciplined for failing to give him prompt treatment.
The trust's first contact was made when relatives wrote a letter two years later. The trust confirmed that no compensation claim was made, but refused to discuss the correspondence.
It's left me horrified to think that I’d put my trust in medical staff and now it’s made me feel they've let me down, they haven't told me the truth and it's very hurtful.
Marion Giles, widow of Grahame A trust spokeswoman said they contact relatives if they have made the complaint that leads to disciplinary action, "in line with the Department of Health's 'Being Open' policy".
In August 2010, a paramedic from the Yorkshire Ambulance Service was struck off over his treatment of three patients including a seven-year-old girl who died in June 2008.
The paramedic pronounced the girl dead without giving her advanced life support treatment - but the complaint was not made by the girl's family.
The Yorkshire Ambulance Service will not say whether the girl's parents know about what happened to their daughter, citing patient confidentiality.
The HPC issued a statement confirming it was aware of "some instances" where families are not told that misconduct hearings are being held.
"We are taking steps to ensure that they are informed of the hearing, where appropriate and in-line with patient confidentiality," it said.
A spokeswoman clarified the statement, saying there is no guarantee that families will be informed, and no attempts will be made to contact relatives of victims where the case has already been heard.
Marion Giles says the HPC's response has made her lose faith in the
National Health Service.
"I just don't know how they could go down that line. I don't know why they're doing that, for what reason? Just to cover their own backs, I presume," she said.
As a result of Sky's findings, the coroner for North Northumberland has launched an investigation into the circumstances of Grahame Giles' death.
"Further information which it seems was not available to the previous coroner, is being clarified before deciding whether to review the case or to hold an inquest," he said.