Duplicating the M1 could cost $2.4 billion, according to a costing released by Labor.
On Tuesday, Opposition Leader Tim Nicholls launched a petition for a second M1 but he would not commit to building it if the Liberal National Party won government.
The first stage of the second M1 would be along an already preserved corridor extending 36.5 kilometres between Stapylton-Jacobs Well Road at Stapylton and Nerang-Broadbeach Road at Nerang, at a cost of $500 million, Mr Nicholls said.
But the Department of Transport and Main Roads estimated the overall cost of the project between Stapylton and Nerang to be at least $2.4 billion, including the cost of land.
Acting Main Roads Minister Steven Miles said the $500 million cited would only pay for part of the LNP’s “stage one”, being Coomera to Helensvale, with the department estimating it would cost $510 million, including land.
WWF conservation scientist Martin Taylor questioned whether a stage two route from Stapylton to Brisbane would go through koala forest.
“If stage two goes through forest then it won’t be called the koala coast any more, it will be the freeway coast,” he said.
“It would be the final nail in the coffin of Queensland’s most important koala population.”
The Goss Labor government’s proposal for an alternative to the Pacific Highway to be built through koala bushland at Logan was widely credited for the Borbidge-led Coalition government gaining power in the mid-’90s.
But Mr Nicholls said Labor had clearly signalled it had no intention of busting congestion on the M1 with its “crazy cost estimate of $2.4 billion – or $65 million a kilometre – for a second route”.
A SEQ Council of Mayors document from May 2016 estimated the cost of a Stapylton to Nerang link at $500 million – or $14 million a kilometre.
The cost could be cheaper than other M1 or Bruce Highway projects because construction occurred outside a live transport corridor, making work more productive and avoiding traffic management costs.
Mr Nicholls also said the proposed route would not go anywhere near koala habitat.
“Any suggestion to the contrary is simply scaremongering,” he said.
On Tuesday, he said the project would tackle congestion on the arterial to the Gold Coast.
“With only a single dual-lane bridge over the Pimpana, Nerang and Coomera rivers, accidents mean the M1 is a parking lot within minutes, demonstrating clearly that an alternative is needed,” he said.
“We want to see a second M1 get under way.”
Dr Miles launched a broadside at the Opposition Leader.
“Tim Nicholls, when he was treasurer of this state, not only failed to invest one single dollar in the M1 but they also failed to plan for the future by taking the unprecedented step to remove the Intra-Regional Transport Corridor from the SEQ Regional Plan in 2014,” Dr Miles said.
“Now he’s given severe underestimates for a project that he wants Labor to build but won’t actually have the intestinal fortitude to back it up and build it himself.”
But Mr Nicholls said south-east Queenslanders were choking on their own fumes because of Labor.
“Being stuck in traffic between Brisbane and the Gold Coast is not only frustrating but an economic handbrake on jobs,” he said.