The four local Labor MPs say they are still trying to find out what is planned.

In fact, Macquarie Fields MP Andrew McDonald, Camden MP Geoff Corrigan, Campbelltown MP Graham West and Wollondilly MP Phil Costa only found out about the proposal through the Advertiser last week.

Dr McDonald said AGL's plan should not be considered under Part 3A of the Environmental Planning and Assessment Act, even though Leafs Gully in Gilead near Rosemeadow was approved under the same legislation.

``AGL did speak to me about a northern expansion in February 2009 before they put in the application,'' he said. ``But the proposed location of the gas plant on the Scenic Hills was not mentioned to me at any stage. I am opposed to the uncontrolled development of the Scenic Hills. I think that piping the gas to existing Rosalind Park plant should be examined.''

Mr Corrigan and Mr Costa said they would seek more information before they commented in any detail.

``Corporate businesses don't keep us in the loop,'' Mr Costa said.

Mr West said: ``I won't support any development that undermines the integrity of the hills [Scenic Hills].''

Cr Oates has spent decades protecting the hills and is determined to make sure the MPs are on side.

``It's really scary that this can happen we're really getting the bad end of the wedge,'' Cr Oates said.

``They're planning to build this next to a school site and we haven't got a clear picture of how big this thing is yet. It seems like everything is falling on deaf ears.''

Cr Oates said the state government needed to get its priorities right, highlighting the need to protect the scenic protection area.

``It makes it difficult to express the community's issues when the powers are no longer in our hands.''

Cr Oates said she urged AGL to find another location to build the gas plant.

``The community will not benefit from this,'' she said.

Team Macarthur is expected to meet this week to devise a plan to stop the proposal from going ahead.