US rapper Macklemore has pledged proceeds from his hit gay anthem to Australia's pro-same sex marriage campaign after the song surged to number one in the country amid a national vote on the issue.

The artist is due to perform his song "Same Love" at the season-ending rugby league grand final in Sydney on Sunday and last week came under fire from some conservative politicians opposed to gay marriage.

They backed a petition calling for his song to be banned from the sports event. The popular track has since become the most downloaded song on Australian iTunes.

The controversy comes as up to 15 million Australians take part in a voluntary postal vote on whether to legalise gay marriage, with the results to be released in mid-November.

"I want to donate my portion of the proceeds from 'Same Love' that I get off that record here in Australia to voting 'yes'," Mackelmore told Channel Nine late Saturday.

The musician was booked to appear in front of the Sydney audience before the nationwide vote was announced, and has vowed to "go harder" after receiving protests from "angry old white dudes".

"It's a testament to where Australia is at right now, in terms of rallying behind the record," he said.

"It gets 'X' amount of signatures to ban me from performing it and there's an overpour of love that is resistance against that hatred."

The heated debate has seen many leading Australian sports organisations come out in support of the "yes" campaign, including the National Rugby League.

Former Australian prime minister Tony Abbott, a leading voice on the "no" side, last week endorsed the petition for the league to withdraw its backing.

"Footy fans shouldn't be subjected to a politicised grand final. Sport is sport!" Abbott tweeted.

This was rejected by Prime Minister Malcolm Turnbull, a supporter of same-sex marriage, who said trying to censor the song "is not consistent with taking a liberal approach to free speech."

"He (Macklemore) should perform whatever he wants to perform," he told Channel Ten TV show The Project. "It's the half-time entertainment at the Grand Final. They've got a great artist. He will sing his top hits, that's one of them. That's great."

Source: AFP