That's why Greg Carter, who runs Cockatoo Rise War Veterans Retreat, believes a royal commission into veteran suicide is vital.

Mr Carter said he returned home from Vietnam with "a very supportive network of people" but he knew most weren't so lucky.

He recalled a heart-breaking phone call he received from a friend who served in Iraq and Afghanistan.

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"He rang and asked if he could have a chat with me and he said one of his mates had suicided," he said.

"It was the 19^th person he served with who had taken their own life in the four years since they'd returned home."

Mr Carter said the number of veteran suicides was grossly underreported in Australia.

"There are so many more than what is reported, there's no doubt about that," he said.

"If the public actually knew how many people who served who had then suicided, they would be staggered."

Mr Carter said on Tuesday that a homeless veteran had recently taken respite at Cockatoo Rise, which is located at the transformed Macarthur Hotel.

"He was recently discharged from the hospital, he isn't in a good way and needed help because hospital staff simply couldn't find him any accommodation," he said.

"In the past week I had three veterans on the one day. One who was a special air service person in Afghanistan who tried to get support back home but after four years, he just gave up.

"Another one later that day said it took him six years to get a pension."

Mr Carter said the lack of support was "appalling".

"These are people who have served in a war zone and have clearly demonstrated they've been in action," he said.

"In real terms it's just not acceptable. Something needs to be done to look into the sheer fact that too many of the people who serve our nation suicide either during their service or afterwards."

Member for South West Coast Roma Britnell said a royal commission into veteran suicides would save and change lives.

Ms Britnell and the Victorian Liberal Nationals announced their support for the inquiry on Tuesday, backing growing calls from RSL Victoria and the veteran community to take action.

"I am in full support of anything that helps our veteran community feel supported and valued," she said.

"I'm fortunate to have seen first-hand the work of RSL Active and the local veterans support centre - they are doing great work, but they can't do it alone.

"A royal commission is the first step in this process. By conducting this process at the federal level, we can ensure an approach that takes into account the stories of all veterans, regardless of where they are from, and lays the foundations for a consistent response across the nation to this critically important issue.

"We can't afford to delay. Because one life lost is one too many."

If you are a current or former ADF member, or a relative, and need counselling or support, contact the Defence All-Hours Support Line on 1800 628 036 or Open Arms on 1800 011 046.