An ABC Four Corners program, aired on Monday night, detailed the officers' trauma, and their continuing struggle for help.

Sufferers who sought compensation say they have been treated like criminals by the insurers.

Brendan Bullock, a decorated former NSW police officer, said he had been left a "broken" man by PTSD but also the treatment he received at the hands of his insurer.

From the beginning of his career in 1999, Mr Bullock was exposed to "extreme acts of violence", suicides and homicides.

The former general duties officer, terrorism investigator and undercover operative for the Australian Crime Commission said he shut away each traumatic incident in his subconscious mind.

But Mr Bullock finally cracked when he attended a murder scene and saw the victim's body hacked to pieces. He left the police force in 2011.

Mr Bullock sought compensation for his illness under the New South Wales Police Force's superannuation fund scheme which was managed by insurer MetLife.

In December 2012, a psychiatrist selected by the insurer found Mr Bullock had "total and permanent" disability because of his acute PTSD.

Yet, the insurer continued to monitor him, despite repeated pleas from the lawyers asking them to desist.

MetLife employed investigators to watch him on another 10 occasions over the next seven months.

Mr Bullock tried to take his own life in 2013, but was found by his wife and daughters.

University of Adelaide's Centre for Traumatic Stress Studies psychiatrist Sandy McFarlane estimated that one in five police officers were at significant risk of mental illness due to their work.

Professor McFarlane, told Four Corners surveillance worsened an officer's PTSD.

He said insurers should not view PTSD as "simply a problem of compensation".

MetLife told Four Corners it had changed its procedures and "now no longer use surveillance in the assessment of claims related to mental illness".

Another former officer suffering from PTSD had private investigators, hired by insurer Employers Mutual, trawl through his Facebook account, downloading 13,427 items in less than a month.

The former officer, identified only as Greg, said his treatment was "humiliating"

His lawyer John Cox said the investigators, from Lee Kelly Commercial Investigations were breaching Section 308H of the NSW Crimes Act when they collected information from Greg's locked social media account.

Lee Kelly Commercial Investigations said it did not breach privacy legislation when collecting data, but declined to comment to the ABC on any breach of Section 308H.

Employers Mutual also declined to comment, referring inquiries to the NSW Workcover authority, now known as Insurance & Care NSW, or icare.

Last year, Victoria's Chief Commissioner Graham Ashton ordered a review following a spate of suicides and a surge in the number of police suffering from PTSD.

It revealed there was a "suck it up" culture which created a widespread mental health crisis within the force.

In Victoria, 35 serving officers have taken their own lives since 1995, including four this year.

In June, the Police Association Victoria and Ambulance Employees Australia called on the Victorian government to introduce legislation that would create a presumption that post-traumatic stress disorder diagnosed in frontline workers was caused by their jobs.

For help or information on mental health issues call Lifeline on 131 114 or beyondblue on 1300 224 636.