Environmentalists, local politicians and community groups have demanded urgent action from the NSW Government to guarantee the safety of the state's remaining disease-free koalas.

Key points: The boundaries of the proposed Georges River national park stretch from Glenfield, south of Sydney, along the Georges River as far south as Appin

The boundaries of the proposed Georges River national park stretch from Glenfield, south of Sydney, along the Georges River as far south as Appin Lendlease has the all clear to begin clearing farm land at Mount Gilead to make way for a 1,700-home housing estate

Lendlease has the all clear to begin clearing farm land at Mount Gilead to make way for a 1,700-home housing estate The Government's Macarthur 2040 plan promises to insulate koalas by managing the boundary between conservation land and urban development

The koalas, south-west of Sydney, are the only population in NSW not afflicted by chlamydia — a disease which affects around 70 per cent of koalas across the country.

Last year, then-Labor leader Luke Foley announced an election pledge to set up a 4,000-hectare national park along the Georges River to protect the unique colony if it won government.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 47 seconds 47 s NSW Labor pledges park for koalas without chlamydia at 2018 state election ( ABC News )

The proposed boundaries of the park stretched from Glenfield, south of Sydney, along the Georges River to as far south as Appin.

It would cover the habitat of hundreds of koalas and safeguard the crucial corridors that allow the animals to travel freely across the region.

But local MPs and environmental and community groups say the park is no closer to becoming a reality, and called on the NSW Liberal Government to adopt the plan to protect the colony from urban development.

Development green lit

State Environment Minister Matthew Kean visited the region last week for a mini summit to inspect the Macarthur colony, which is estimated to consist of around 500 koalas.

The member for the Federal seat of Macarthur, Mike Freelander, said he invited the Minister to the region to see firsthand the impact of infrastructure development.

In July, Lendlease was given the all clear to begin clearing farm land at Mount Gilead to make way for a 1,700-home housing estate.

Stage one of the proposed park. The west bank of the Georges River is in yellow, and stage two, Gilead, in red is already slated for development. ( Supplied: Total Environment Centre )

It is the first stage of the State Government's plan to add 35,000 new homes to the region.

Its Macarthur 2040 plan promises to insulate koalas from the development by managing the boundary between conservation land and urban development.

But Mr Freelander said it was not enough, and the State Government should also commit to a national park to stop infrastructure expansion from destroying koala habitats.

"This region's thriving koala colony has been put at risk because of the very rapid development of housing," Mr Freelander said.

"We need the Government, the NSW Liberal National parties, to support a national park for our koalas.

"We don't want to have this continual urban sprawl impacting our wildlife, and I think the State Government needs to look at how we're going to protect the environment."

Campbelltown MP Greg Warren also attended the meeting and echoed the concerns.

"The Government doesn't have a good track record when it comes to conservation and preservation of habitat and wildlife," he said.

"We need action now and we need to see it backed up with the appropriate measures for preservation and conservation to ensure that our koala colony thrives."

Recovering population

The koalas are part of a recovering population, returning to habitats they previously occupied but were forced to move out of when the land was cleared.

Saul Deane from the Total Environment Centre said it was a great program that the State Government should be embracing.

"While we have koala colonies disappearing across the state, here we have koalas moving back into land that they once existed in," Mr Deane said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 48 seconds 48 s Making its way across a koala-safe fence at Hawks Nest, north of Newcastle

He said koalas were returning to these areas at the same time developers were moving in, causing problems for planners and the Government.

The Mt Gilead development sits right in the middle of two crucial koala corridors — the Georges River and the Nepean River.

Mr Deane said for the recovery process to continue the animals needed to be able to travel freely between the two water sources.

"The biggest problem we have with protecting these populations and enabling them to survive is making sure they're connected and can move through the landscape," he said.

"It's very important in securing these koalas' future."

Park expansion

The Total Environment Centre has also called for the proposed boundaries of the park to be extended further south to include Wilton, the home of another disease-free koala colony that is also threatened by development.

The south-east Wilton development plans to add 16,500 new homes to the region in the next 20 years.

Last week, the Joint Regional Planning Panel voted in favour of approving the first stage of the development — green lighting the subdivision of 700 residential lots along Picton Road.

This decision was reached despite the community's concerns about inadequate infrastructure, the impact on ground water supply, and the lack of consideration for the local koala habitat.

Mr Deane said maintaining a corridor from the Wilton colony and the Macarthur colony would allow koalas to have the space and freedom to continue to thrive.

"At the moment koalas are disease-free in these two areas because they've come from a small base, and they're moving into areas they previously occupied," he said.

"We need to send a message that koalas are really important to us as a community and we will put their protection first before we develop more subdivisions."