LABOR has boosted the fortunes of a parliamentary motion setting the scene for gay marriage by endorsing the measure when it comes to a vote this week.

The motion, moved by Greens MP Adam Bandt, will also be supported by fellow crossbenchers Andrew Wilkie and Tony Windsor, but opposed by the Coalition and Queenslander Bob Katter.

Labor agreed to endorse the motion after it was amended on Monday night to remove a conflict with the party's platform, which does not support gay marriage.

The motion now calls on parliamentarians to consult their electorates about attitudes to gay marriage. Its fate now rests with New South Wales rural independent Rob Oakeshott, who is progressive on social issues, and Western Australian National Tony Crook.