A re-elected Labor government would invest $1 billion into mental health services across Australia, in what the nation’s peak mental health body has labelled a "landmark investment."

The commitment includes $225 million to deliver 21 new Medicare Mental Health Centres and upgrade 10 centres across the country, many of those in regional centres.

There would also be $200 million to expand Headspace services, $500 million for Youth Specialist Care Centres and $90 million to train 1,200 new mental health professionals.