In one case, a paramedic smuggled fentanyl, a highly addictive painkiller, home in a secret pocket they had sewn into the leg of their pants.

Another admitted stealing almost 100 vials of fentanyl stolen from different ambulance stations at a time when they could enter any office using a master key and access unlocked ambulances.

The Independent Broad-based Anti-corruption Commission probe highlighted a culture of self-protection and denial among the 22 paramedics it investigated.

Just prior to the IBAC inquiry starting in November 2015, one paramedic admitted to deleting all text messages with a colleague who had stolen fentanyl from work and later died from an overdose.

They also deleted all messages that referred to IBAC.

"At the time it seemed like deleting links [with their colleague who had died] was an appropriate or normal thing to do," the paramedic said.

Most of the 22 paramedics investigated worked in Barwon South West, a region taking in Geelong, Warrnambool and the Surf Coast, as part of Operation Tone.

The probe alleged:

• An advanced life-support paramedic admitted to using and selling illicit drugs to friends and denied it was trafficking. They told IBAC: "I have given drugs, yes, in exchange for money, there's a difference between [that and] trafficking".
• A clinical instructor who started using fentanyl in 2015 would source residual amounts from Ambulance Victoria sharps containers drawn into a syringe to avoid detection and, if they had time, replace it with saline. They would source fentanyl from different branches, transporting it from work to home in a false pocket in their pants.
• A former paramedic charged with stealing fentanyl told IBAC last year they went to different ambulance stations on at least 25 occasions and estimated they'd stolen about 90 vials. At the time, paramedics could enter any station using a master key and access unlocked ambulances.
• An advanced life-support paramedic, clinical instructor and educator admitted to stealing IV drips for their children to relieve their hangovers.

One paramedic was sacked and eight resigned while under investigation, IBAC said. Six paramedics kept their jobs, but were transferred or enrolled into ethics courses.

Despite the focus on one area, IBAC said it considered similar conduct and "corruption vulnerabilities" were likely to be widespread across Ambulance Victoria.

Ambulance Employees Association secretary Steve McGhie said the report was a slur against all paramedics.

"If IBAC thought that was happening [drug abuse and corruption], I would've thought that would be a more extensive investigation and a bigger report," Mr McGhie said.

He said a small cohort made serious errors of judgement but for others, their behaviour was indicative of the mental health of the workforce.

The suicide rate among paramedics was three times higher than police or firefighters, the Victorian coroner's court found in 2015, and IBAC said some paramedics were using drugs to deal with psychological issues. They were also reluctant to seek help for fear of repercussions on their careers.

A former paramedic told the watchdog that most who did speak up if they or a colleague had a drug problem were "pretty much sacked straight away".

In one case, a paramedic who had self-reported they'd stolen fentanyl was subsequently dismissed and later died from a suspected drug overdose, the report claimed.

Ambulance Victoria chief executive Tony Walker said the report was a "wake-up call". He said a number of significant changes have been made over the past two years including targeted drug testing and a robust drug and alcohol policy.

He said that while the IBAC report focused on the actions of paramedics in the Barwon South region, that illicit drug-taking among ambulance staff likely occurred in other parts of the state.

Security around drugs has also been improved including swipe cards and CCTV cameras at each branch.

Fentanyl is 100 times more powerful than morphine. Since 2012, fentanyl or morphine have been involved in three paramedic deaths in Victoria.

IBAC called on the Department of Health and Human Services to address similar vulnerabilities in other Victorian health sectors. Last week, a Melbourne drug counsellor was charged with trafficking.

Fairfax Media revealed five years ago that fentanyl was being siphoned-off and a large amount of the drug had gone missing from ambulance stores.