Leading Australian mental health organisation beyondblue has called for marriage equality, citing high levels of stigma and discrimination towards LGBTI Australians.
In a statement released on Tuesday, beyondblue said that excluding same-sex couples from marriage is discriminatory, and fuels hurt and stigma.
"For those who love, but are not allowed to marry, their sense of loss, hurt, stigma and discrimination is profound."
"Allowing same sex marriages will not make any difference to the lives of the majority, including married heterosexuals, but it will make a great deal of difference to those who seek same sex unions."
The open letter was signed by chairman Jeff Kennett and the entire beyondblue board, including tv presenter and swimmer Johanna Griggs, and and former prime minister Julia Gillard.
Gillard, who supported the traditional definition of marriage throughout her time in government, announced her support for the reform just last week.
Beyondblue chairman Jeff Kennett told BuzzFeed News the organisation felt compelled to speak out as they know "first hand" the effects of discrimination on LGBTI people.
"We as a board, regardless of our politics, colour, race or age, simply say to all politicians: please understand while this may not be a tenth order issue for Australia, or a hundredth order issue, to those who are gay, who wish to exercise the same rights as heterosexuals, you are causing pain, you are discriminating," he said.
The statement references the increased risk of depression, anxiety, substance abuse and suicide among LGBTI people.
"This is not because of sexuality or gender identity. LGBTI people, just like any Australian, face the same risk factors for mental illness and suicide," the statement reads.
"What is different is the violence, prejudice and discrimination they face, simply for being who they are."
Kennett dismissed the concerns of marriage equality critics who argue you can support ending discrimination against LGBTI people while not supporting marriage equality.
"I'd say very simply, to those of us who are heterosexuals, who can enter into marriage because of our feelings for one another, without even getting any permission, it doesn't affect us at all," he said.
"This is not a political issue, this is one of equity. This is one of applying the anti-discrimination laws evenly."
"If you believe that discrimination is wrong, then end discrimination. You can do it with the stroke of a pen today."