Western Sydney Labor MPs set to change vote to support same-sex marriage in Parliament.

Three Federal Labor MPs representing western Sydney electorates have confirmed they could switch their votes in Parliament to support gay marriage.

Chris Bowen, Ed Husic and Julie Owens were among the 98 MPs across the House of Representatives who helped vote down the same-sex marriage bill in the last parliament.

All three have declared this week they could change their vote and back a bill.

Mr Bowen, the member for McMahon and shadow treasurer, has said if the Labor Party still has a conscience vote he will change his positionbecause marriage is a right for all citizens.

Mr Husic, who holds the seat of Chifley, has told Fairfax he is also in favour of legalising the unions.

He said he had never personally opposed same-sex marriage and was reflecting a view held in his electorate at the time of the previous vote.

Member for Parramatta Ms Owens told the ABC if there was a conscience vote on both sides of Parliament, she would find it “almost impossible” to vote against same-sex marriage.

She said she had always privately supported it, but wanted to reflect the views of her electorate when she voted in 2012.

Gay marriage was considered a divisive issue in the lead-up to the last election, and western Sydney was a key battleground for both parties.

All three MPs said the freedom to choose through a conscience vote is an important condition for their support.

Deputy Labor leader Tanya Plibersek has been pushing for the Opposition to change its formal positionand agree to a binding vote on same-sex marriage instead.

That is at odds with Opposition Leader Bill Shorten, who wants a conscience vote to remain in place.

Some same-sex marriage advocates within the Coalition are warning if Labor moves to a binding vote it will make it less likely for the Liberal Party to allow internal consideration of allowing a conscience vote.

This post originally appeared on ABC Online.