On May 30 the clinical leader at headspace Dubbo warned that exclusion and discrimination were responsible for an elevated level of mental health problems in Lesbian, Gay, Bisexual, Transgender, Intersex, Questioning and Asexual (LGBTIQA) populations.

She said their rate of suicidality-suicidal throughts, attempts and death by suicide- was 14 times higher than heterosexual peers.

Ms Hartley urged all levels of the community and government to "promote sexuality and gender equality and inclusion".

"A lack of marriage equality is treating LGBTIQA people as legally unequal to heterosexual peers by not allowing them the same life choices," she said.

On June 5 the coalition of mental health organisations used similar arguments in telling "all political parties" of its expectation that they would approve marriage equality legislation.

Black Dog Institute, headspace, Spur Projects, Mental Illness Fellowship of Queensland, Suicide Prevention Australia, ReachOut Australia, Roses in the Ocean, the JED Project and Batyr have all submitted open letters to the federal government.

Mental Health First Aid Australia has endorsed the initiative.

"The fact is that the rate of attempted suicide amongst lesbian, gay, bisexual and transgender people is currently 14 times the national average," said coalition spokesman Lee Crockford of Spur Projects.

"This is utterly shameful. The big contributing factors are exclusion and discrimination. It has to stop."

Mr Crockford said marriage equality was "much more than a piece of paper".

"It's a vital step to increase mental well-being and reduce suicide," he said.

On June 1 Federal Labor Party leader Bill Shorten introduced a marriage equality bill to the Federal Parliament.

The House of Representatives voted to adjourn debate on the bill.

The federal coalition has proposed a cross-party bill on the issue.