An investigation into the death of a New South Wales paramedic has raised questions about how the Ambulance Service monitors access to restricted drugs.

Tony Jenkins took his own life a short time after he was confronted with allegations of opioid theft and drug tampering.

Now key evidence in the case has been withdrawn, and a New South Wales Ambulance investigation has revealed widespread drug abuse within the service and a breakdown in the safekeeping of highly restricted medication.

'I was suspicious'

In April, Sharon Jenkins received the worst news of her life.

Her husband Tony, who had been a paramedic for 28 years, had taken his own life.

It happened just hours after he had apparently admitted to his managers that he was addicted to opioids.

Eight months later, holes began to emerge in that story.

Sharon Jenkins said the Ambulance Service withdrawing the reference to morphine in its investigation into Tony's death "puts everything into question". ( ABC News: Laura Brierley Newton )

"I was shocked and horrified — they've changed key evidence regarding drug possession," Ms Jenkins told the ABC's The World Today.

Immediately after Tony Jenkins' death, the New South Wales Ambulance Service did an investigation known as a root cause analysis.

Tony Jenkins with his two daughters. ( Supplied )

It stated that the Newcastle paramedic had handed over two syringes with morphine during that meeting with his managers.

Sharon Jenkins said she never believed that, and she wanted to know more.

"I asked where those syringes are now; were they tested, what was in them, who else sighted them — obvious questions," she said.

"I was suspicious that Tony would have two syringes full of morphine in his pockets."

'Scapegoated': Family wants an inquest

Last week, the NSW Ambulance Service wrote to Sharon Jenkins, withdrawing the reference to the morphine.

"The description of events was in error," the letter said.

"The root cause analysis team records do not indicate that paramedic A ever handed over the vials to managers."

Sharon Jenkins was astonished.

Tony and Sharon Jenkins as a young couple. ( Supplied )

"That was the actual only physical evidence we were offered and we did take that as fact," she said.

"It puts everything into question now.

"This is an unacceptable level of incompetence and mismanagement.

"The family more than ever see it's very important that we have a coronial inquest so all these things can be looked at and brought out in a public manner."

For Sharon Jenkins, questions remain.

"Tony is now not here to defend himself and we've had to accept what they've told us as fact, but now we find out it is actually fabrication.

"So yes, I believe he was scapegoated for a huge problem in the Hunter with fentanyl being compromised," Ms Jenkins said.

A police brief to the New South Wales coroner about Tony Jenkins' death is now being finalised.

Report shows widespread opioid use

In a statement, the NSW Ambulance Service has acknowledged the mistake, but says the error does not change the recommendations from the report.

The ABC has obtained a copy of the root cause analysis done about the Jenkins case.

It contains startling details about widespread use of morphine and other highly addictive opioids like fentanyl across ambulance stations in New South Wales.

Fentanyl comes in a number of different forms including slow-release patches, nasal sprays, injectable formulations, tablets, and lozenges. ( Weibo: Directors and Boards Magazine )

The 18-page report says an audit of fentanyl stock at stations in the Hunter region found that over 10 per cent had been compromised.

That usually means it had been diluted with another liquid, possibly water.

The report also says a state-wide audit has found that fentanyl vials have been tampered with in other parts of New South Wales.

And it also details systematic violations of protocols for the safekeeping of all restricted drugs.

The NSW Ambulance Service is updating its 15-year-old policy for dealing with drug and alcohol abuse by staff.

In a statement it says it is on track to implement recommendations to improve the wellbeing of its staff.