The Greens could lose their bid for the seat of Melbourne because of a history of snubbing the Sex Party.
Preferences will be crucial in determining Saturday's by-election result, and the Sex Party will direct its preferences to Labor.
Sex Party candidate Fiona Patten said she was concerned by the "anti-sex feminist" element in the Greens.
A poll conducted this week by ReachTEL found that Ms Patten was attracting 6.1 per cent support, putting her in third place.
Greens candidate Cathy Oke was leading on 38.1 per cent, marginally ahead of Labor's Jennifer Kanis on 36.5 per cent.
This would mean the outcome would be decided by the preferences of those who vote for Ms Patten and other minor candidates.
This week's poll found that one in four voters would support a candidate other than Dr Oke or Ms Kanis.
More than 10,000 votes that went to the Liberals in Melbourne at the 2010 election are up for grabs after the party's decision not to stand.
Ms Patten said the stand-offish attitude from the Greens dates back to the 2010 election, and the influence of a moralist element in the party.
"We have been concerned about this Left-wing anti-sex feminist position," Ms Patten said.
"It's not that uncommon for the extreme Left to have very moralistic positions when it comes to sex."
In the lead-up to this year's Niddrie by-election, the Greens preferenced the Sex Party second-last before negotiations could take place, Ms Patten said.
This time, the Sex Party has directed its preferences to Labor without talking to the Greens.
"I hope we will be able to work with them in the future," Ms Patten said.
In addition to campaigning for sex industry reform, the party supports drug decriminalisation, secular education, greater privacy protection and 24-hour public transport on weekends.
A spokesman for the Greens said voters were free to choose where to direct their preferences.
"The key thing to remember about preferences is that the voter gets to choose," the spokesman said.
"We urge everyone to consider their vote carefully when they fill in their ballot, and don't think that you have to follow any party line."
Source: Herald Sun