MALCOLM Turnbull has said that if he were allowed a free vote he would be likely to support gay marriage legislation.

The Liberal frontbencher's statement - the first time he has gone so far on his view - has highlighted the refusal of Opposition Leader Tony Abbott to allow a conscience vote, as Parliament considers private members' legislation to legalise gay marriage.

Pressed on Sky TV Mr Turnbull said: ''If there was a conscience vote on this issue, subject to the legislation being satisfactory … I would be more likely to support it than not.

''But politics is a team sport - we have decided on our side not to have a conscience vote on this issue … so I won't be crossing the floor.'' While backbenchers can cross the floor, Mr Turnbull would have to quit the frontbench if he did so.