Act leader John Banks will vote for a bill aimed at legalising same-sex marriage, in a reversal of his past opposition to increased legal rights for gay people.
Mr Banks today revealed he would vote for Labour MP Louisa Wall's marriage equality bill at its first reading in Parliament on Wednesday.
When asked why he was supporting the bill, he said "because I am".
His support strengthens predictions the bill will pass at first reading and progress to select committee stage.
Mr Banks has previously been a vocal opponent of homosexual law reform.