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.