Tim Minchin has mocked the Turnbull government's decision to hold a non-binding postal vote on same-sex marriage in a pithy music video uploaded to his social media channels.

The Australian composer and comedian has reworked Peter Allen's classic song I Still Call Australia Home into a tune called I Still Call Australia Homophobic.

Minchin recorded the song on his iPhone and uploaded the video to Facebook on Friday morning. He said he penned the "heartfelt song to my homeland" to encourage all Australians to vote for equality.

"No matter how far or how wide I roam, I still call Australia ... homophobic," Minchin says in his song.