Campbelltown Council will write to state environment minister Matt Kean requesting immediate support to protect local koala populations.
Councillor Karen Hunt raised the motion at last night's meeting, garnering support from her fellow councillors.
She said she was inspired to raise the motion after reading of Mr Kean's intentions to double the koala population by 2050.
Mr Kean made the comments following the release of an inquiry which revealed the state's koalas would be extinct in the wild by 2050 without immediate government intervention to safeguard their existence.
Cr Hunt asked the council to write to Mr Kean requesting "the NSW state government provide immediate support for the preservation and protection of the Campbelltown and south-west koala colonies and habitats by commencing construction of viable, safe and effective crossing points across Appin Road together with the requisite flexi-fencing along Appin Road".
"I got a lot of support, everyone was in favour of the motion and nobody spoke against it," she said.
"I emphasised that we've been waiting and waiting for the government to do something about our koala colony, to protect them.
"So I thought we should take the opportunity with this being the fifth environment minister [we've contacted] that we might get someone who is going to start to do something."
Cr Hunt said the council had long called for underpasses and appropriate fencing.
"That's been our request from the get-go, the whole council has called for that," she said.
"The [underpasses] need to move east-west, we don't want the koalas getting cut off from going across Appin Road - that's their habitat, that's their corridor to go to the Nepean.
"There's no reason that the government couldn't start to do underpasses now, before they widen Appin Road, and make them wide enough for a four-lane road.
"I can't see why it can't be done right now. We're losing too many koalas as it is.
"The north coast already has these things."
Cr Hunt said it was also important that fencing along Appin Road is different to the fencing provided on Picton Road, which she called "a joke of a fence with openings straight out onto the road".
She said the council needed a response from Mr Kean "sooner rather than later".
"That's what I'm hoping, but I'm not going to hold my breath."