If it was his decision, Barry O'Farrell would allow the coalition a conscience vote on same-sex marriage, the New South Wales premier confirmed Wednesday.

O'Farrell joins South Australian Liberal leader Isobel Redmond in support of a coalition conscience vote on same-sex marriage. He leads the strongest coalition government in the country with a majority of seats in the state's lower house.

The NSW premier expressed his support Wednesday in response to the following tweet from Australian Marriage Equality National Convener Alex Greenwich on the issue:

Alex Greenwich: @Barryofarrell what are your thoughts on a coalition conscience vote on marriage equality?

Barry O'Farrell: @AlexGreenwich that's how it would be handled if it was the issue before the NSW Parliament.

Greenwich welcomed the premier's comments.

"The premier knows that there is growing support for marriage equality within the coalition, and understands the importance of allowing that support to be expressed," he said.

The premier’s statement comes as there is growing pressure within the Federal Coalition on Tony Abbott to allow a conscience vote on the issue.

Liberal MPs Malcolm Turnbull, Teresa Gambaro, and Joe Hockey all recently surveyed their electorates on issue and found overwhelming support for reform.

Greenwich warned Abbott about not allowing MPs to express their constituent's views.

"Mr Abbott would be putting key MPs in a very precarious position at the next election if he forced them to vote against the overwhelming wishes of their constituents,” Greenwich said.