YARRA Greens and Socialists have entered into a "marriage of convenience" by choosing to preference each other over the ALP in this month's election.
The two parties have been involved in a series of long-running disputes this term, especially over planning and environment issues.
Greens candidate and incumbent councillor Amanda Stone said although she found Socialists Stephen Jolly and Anthony Main's behaviour at some council meetings "appalling", politically they were a better match than the ALP.
"I've always been ambivalent about the Socialists but their policies are more aligned to ours," she said. "This isn't about personalities."
Cr Stephen Jolly urged Cr Stone to "stick to the policies and leave out personal attacks".
The Socialists give preference to the most left policies, he said, so they picked the Greens above the ALP.
Yarra mayor and ALP candidate Geoff Barbour said he was disappointed by the deal but rejected suggestions it would affect his party's chance of success later this month.
"I was a bit surprised by the deal as they seem not to be on good terms with each other in council," he said.
"However, we will be out there campaigning solidly."
He expects at least one ALP candidate will be elected to each of the three wards.
The Greens and ALP have agreed since 2008 to occupy the mayor's position and pass it on to the other party.
The current council is made up of three Greens, two ALP, two Socialists and two independents. Twenty one candidates have nominated, with Josh Funder the only incumbent not seeking another term.
Yarra residents and ratepayers will vote in person on October 27.