Pop Singer Katy Perry has told Opposition Leader Tony Abbott she wouldn't vote for him because of his stance on gay marriage.

"I love you as a human being but I can't give you my vote," Perry told Mr Abbott on Sydney's 2DayFM, after being informed he opposed same-sex marriage.

Mr Abbott was one of a number of Aussie "celebrities" given the chance to ask the US pop star a question on Thursday.

He said his "big question" was when would the 28-year-old singer again tour Australia.