But Aaron Rule and Judy Hannan have a tough job ahead of them.

Of 669 state-significant and major project applications made to the Planning Department and Minister Frank Sartor since 2005, 625 were approved. On paper, this gives the local councils and community protesters only a 6.6per cent chance that AGL's gas-plant proposal will be refused.

Last week, the Advertiser reported a proposal for a smaller version of AGL's proposed gas-fired power station is to be lodged after the previous plans were withdrawn by the power company in February 2007, just before the last state election.

An AGL spokesman said: "While the original air quality levels were well within established guidelines, halving [the size of] the plant would reduce them even further.''

Campbelltown Mayor Aaron Rule and Wollondilly Mayor Judy Hannan said their councils would work as a combined team to fight the controversial proposal.

"It's well known that our neighbouring council Wollondilly has been opposed to this development and Campbelltown is happy to join with them in their opposition,'' Cr Rule said on Monday.

"As a region we're clearly united in a single voice.

"This must send a very strong message across local government lines, regardless of anything else.''

Cr Hannan is furious it is back on the agenda.

"We were told [before the last election] it was off but I've been told by the gas people it was never withdrawn only withdrawn to change it.''

State Labor MP Phil Costa, too, said he is determined to make his opposition heard.

He said better sites could be found, such as Marulan.

"If Frank [Sartor] goes to a public enquiry that'll give us the chance to really air it openly,'' he told them.

"We have to focus on the valley and air quality because we want to win the debate you don't get that combination in many other places. I told Frank it was a hot potato and I don't want it.''