LGBTQI groups are backing the Indigenous Voice to parliament, saying it's time to pay forward the support they received in achieving marriage equality.

On Wednesday, 22 LGBTQI groups from across Australia declared their support for the Voice as the country draws nearer to a referendum towards the end of this year.

Equality Australia said there were many parallels between the successful 2017 postal survey that led to marriage equality, and the push for an Indigenous Voice.

In the 2017 survey, 7,817,247 people - or 61.6 per cent of those who responded - said Yes to marriage equality.

"When there was a public vote about our lives, the majority of Australians had our back and it's time to pay it forward," Equality Australia legal director Ghassan Kassisieh said.

"We know that laws and policies are better when governments listen to the voices of people who are most affected."

BlaQ Aboriginal Corporation chief executive Shane Sturgiss said those in the Indigenous LGBTQI community were no strangers to the fight for equality.

"This is the second time our community has had the entire nation eyeballing them, knowing that conversations are being had about them in homes around the country and not all of them are favourable," he said.

"A Yes vote in the referendum will ensure First Nations people are recognised, bringing a level of fairness and equality that has not been seen in Australia before."

An online survey by Equality Australia canvassing 4078 of its supporters found almost 90 per cent said they would vote Yes for the Voice, while 231 planned to vote No and 171 people were unsure.

Gil Beckwith from Sydney Gay and Lesbian Mardi Gras said the Voice aligned well with the event's core values of diversity, inclusion, and empowerment.

"We stand for giving a platform to under-represented voices, and supporting the Voice to parliament is a crucial and natural extension of our commitment to celebrate all facets of our community," Ms Beckworth said."

Duncan Murray - AAP