Chief of Army, Lieutenant General David Morrison.

Chief of Army, Lieutenant General David Morrison speaks to the media during a press conference in Canberra. Photo: Alex Ellinghausen

Seventeen Defence personnel, including officers, are under investigation in relation to explicit emails that denigrate women.

In announcing the investigation at a press conference in Canberra, Chief of the Army, Lieutenant-General David Morrison, said the allegations being examined were "disgraceful" and "worse than the Skype scandal" that hit Defence in 2011.

General Morrison said he had already spoken to four of the women who were victims of the emails and imagery, and said that there were several other victims.

"They were angry, they were concerned," he said.

There are also suggestions that illicit drug use may also be involved.

The Army chief lamented that the email claims came after significant efforts to encourage women to join and stay in the Army.

''I'm appalled at this situation,'' General Morrison said.

General Morrison said that three service members have already been suspended and may be persons of interest to the NSW Police.

Five personnel are under consideration for suspension and evidence is being collected in relation to a further nine.

He told reporters that a broader group of about 90 Defence personnel - overwhelmingly from the Army - may be on the periphery of the group involved in the email exchange.

General Morrison says the allegations involve the production and distribution of ''highly inappropriate'' material across both defence computer systems and the public internet over the past three years.

The Army chief said he was keeping an open mind about the investigation, but added "I view the allegations that are being made in the gravest light".

He said the claims brought the Army into disrepute and he was resolved that, if proven, every possible step would be taken to remove the perpetrators.

General Morrison said he was not able to go into detail about the emails and photos but said they were explicit, derogatory and demeaning and ''repugnant to me''.

When asked if the latest allegations were a repeat of the Skype scandal, he was it was "worse".

The so-called ''Skype scandal'' refers to an incident in 2011 when a cadet, known as Kate, discovered her sexual encounter with another cadet had allegedly been streamed, without her consent, via Skype to other male cadets.

It prompted wide-ranging reviews into abuse within Defence, and calls for cultural change within the military.

General Morrison said the group under investigation includes a lieutenant colonel, majors, captains and warrant officers.

It is understood that the female victims include ADF personnel, public servants and members of the broader public.

General Morrison said he was not able to answer how the incident came to the attention of authorities.

But he said that the Australian Defence Force Investigative Service told ADF chief David Hurley about the incident on April 10.

General Morrison was overseas at the time but was told when he returned soon after. Defence Minister Stephen Smith was also informed around this time.

General Morrison said that Defence leadership no longer accepted the ''bad apple'' argument within its ranks.

''The Army is changing and what you are seeing today is evidence of that change and my commitment to transparency.''

with AAP

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