Prime Minister Malcolm Turnbull has reignited criticism of his government's same-sex marriage policy after posting on social media to celebrate Valentine's Day.

Mr Turnbull, who supports the reform of marriage, posted a photo of himself and his wife Lucy, a businesswoman and former lord mayor of Sydney.

The Prime Minister wrote: "When I first asked Lucy to marry me, she said, 'Let's wait until we grow up.' Well we didn't wait long and now it is almost impossible to imagine, let alone remember, what it was like not to be together, so much so that I have a much clearer sense of 'Lucy and me' than I do of 'me'."

While many responses were positive, others were disappointed and angered with Mr Turnbull's stance since becoming leader.