Australia's army chief has called for the recruitment of more women, gays and ethnic minorities in the military, saying the country's changing demographics make it unsustainable not to.

In a speech to the Sydney Institute, Lieutenant General David Morrison said the defence force, which last year was stung by revelations about sex scandals and abuse, had to preserve its strong combat culture.

"But we also need to concede that this culture has tended to exclude women and some ethnic groups who are under-represented in our ranks," he said late Tuesday.

"This will prove unsustainable with the demographic changes that are occurring in this country over the forthcoming decade."

The Australian Defence Force has been rocked by a string of sex scandals, including a case in which a young female cadet was unknowingly filmed having sex with another cadet and the images were broadcast to her classmates.

The incident prompted a series of reviews of the armed forces, and the military has taken steps to overhaul its culture and has recently announced that women will be able to take on all defence roles, including combat ones.

Morrison said he was passionately committed to expanding the presence of women within the army, and said removing the few formal impediments which prevented them from taking up combat roles would not undermine performance.

He added that there was much momentum for change within the defence force.

"I think that a lot of our women are impatient for this and are very appropriately pushing for it to happen. And that's terrific and we will give them every opportunity to do that," he said.

"Will it cancel out and negate any unfortunate incidents in the future? Unlikely. Human nature is human nature, irrespective of whether it's lived in uniform or without."

Morrison said change was occurring, noting that when he joined the army some 25 years ago "the reaction to people of a different sexual orientation would have been seen as almost insurmountable I think by army's hierachy".

"And yet now of course it isn't an issue and nor should it be," he said.

"And we have many very proud gay and lesbian soldiers, airmen, airwomen, sailors, serving in our Australian Defence Force and we're very proud of their efforts as well."