The Federal Government is promising to allocate $350 million in the federal budget to help prevent suicide among war veterans.

The multi-million-dollar package would be the biggest federal funding injection in decades, and would go towards existing services, suicide prevention programs and better data collection, Minister for Veteran's Affairs Dan Tehan said.

The money is to be set aside in Tuesday's budget targeting a raft of mental health conditions, including post-traumatic stress disorder (PTSD), anxiety, depression and bipolar disorder.

The money would also target substance abuse and alcoholism.

Mr Tehan said younger veterans were particularly vulnerable.

"Those who leave the military aged between 18 to 28 are more susceptible to suicide than those in the older cohort," he said.

"We want to make sure that our veterans, once they leave the military, get the support they need to transition to civilian life."

A Senate inquiry investigating suicide by veterans and ex-service personnel received hundreds of submissions.

The rate of suicide among veterans is thought to be higher than that of the general population, but specialists told the inquiry in February there is no clear data because of reporting.

Mr Tehan said funding would be allocated to existing services, suicide prevention programs and better data collection.

"The best way we can honour the service and sacrifice of the veterans is to make sure that we are looking after veterans of today," he said.

"Mental health and the incidence of suicide are areas where we must break down the stigma.

"The best thing anyone can do is to make sure that they get support very early on, so people can get that support straight away and this service makes sure those services are available immediately."