Prime Minister Malcolm Turnbull managed to get his signature energy policy through his party room but now he could have a fight on his hands to get it through parliament.
Up to a dozen coalition members have identified concerns with the plan.
Tony Abbott, George Christensen and Andrew Hastie have reserved their right to cross the floor and vote against the policy.
Others publicly raising issues include Craig Kelly, Tony Pasin, Eric Abetz, Barry O'Sullivan, Kevin Andrews and Andrew Gee, while Barnaby Joyce has signalled specific amendments he wants to see.
With a tight majority in the lower house, questions are being raised about whether the policy can make it over its next hurdle.
Commonwealth legislation is expected to be introduced to parliament before the end of next week.
Mr Turnbull is reportedly considering further legislation to keep internal critics on side and met with five of those MPs late on Tuesday.
The Australian says it's understood that legislation would lock in a price guarantee, separate from the NEG's emissions target and reliability guarantee, to address concerns the policy has no firm mechanism to lower prices.
ACT Energy Minister Shane Rattenbury questioned whether the government could get it through, saying the final outcome could come down to how the federal Labor votes.
If the opposition sides with the government, the bill will move to the Senate but if not the outcome will depend on the coalition's final numbers in the lower house.
"A handful (of coalition MPs) indicated they may cross the floor and given the relatively close numbers, it does beg the question," Mr Rattenbury told AAP.
After Mr Turnbull secured party room support for the plan, state and territory ministers agreed in a phone hook-up on Tuesday night to put draft state legislation out for consultation from Wednesday morning.
Ahead of the call they were given copies of the commonwealth legislation, which Mr Rattenbury said had raised further concerns around the emissions reduction target.
It has been a consistent issue for the ACT, Victoria and Queensland governments, who have so far refused to give their support for the energy plan.
The draft laws would exclude Western Australia and the Northern Territory from the whole scheme, including the emissions reduction target rather than just the reliability requirement as had been previously thought.
Mr Rattenbury also raised concerns about an apparent lack of willingness by the federal government to negotiate with them.
He said it would be a "far more fertile strategy" for Energy Minister Josh Frydenberg to start talking to states and territories about their issues than to deal with the "hardcore of his backbench".
"We will reach a point of political stalemate," he warned.
© AAP 2018 Photo credit: AAP Image/Lukas Coch