The Coalition party room has approved the Prime Minister’s plan for a national energy guarantee.

After nearly two-and-a-half hours of debate on Tuesday, Liberal and National MPs endorsed the NEG, but former prime minister Tony Abbott has expressed strong concern about it.

According to the ABC, he and three colleagues – Andrew Hastie, George Christensen and Eric Abetz – have reserved their position on the legislation, meaning they could cross the floor to vote against it.

Malcolm Turnbull was forced to stare down a handful of backbench Coalition rebels railing against his signature energy policy, saying on Monday that “ideology and idiocy” could not be allowed to determine its fate. Later he described support for the policy in the party room as “overwhelming”.

“This policy is part of our suite of measures that is already seeing us turning the corner on electricity prices,” he said.

Starting in 2020, the NEG is designed to bring down energy bills by about $550 a year. It requires retailers to source electricity that meets reliability and Paris Agreement emissions reduction targets.

But Mr Abbott had argued Coalition MPs would be “dead wrong” to approve it.

“Any attempt to kind of ram this through the party room … would be dead wrong,” he told ABC television’s 7.30 on Monday.

Andrew Hastie, Eric Abetx and Tony Abbott are united in their opposition to the national energy guarantee. Photo: AAP

Liberal backbencher Tony Pasin said he could not support a NEG without a price target. He described the assumptions in the NEG modelling about the price of power falling as “brave” and said he wanted to see a target or Government expectation that prices would fall.

Former deputy prime minister Barnaby Joyce has also proposed an amendment to enforce price reductions.

The legislation setting an emissions reduction target of 26 per cent on 2005 levels by 2030 for the electricity sector is expected to be put to a teleconference of state energy ministers later on Tuesday.

The states will be asked to agree to a four-week consultation process.

As well as rolling out the NEG, the Turnbull government is expected to underwrite new power generation projects, which could include coal-fired plants.

Mr Turnbull has promised to underwrite new power generation projects – which might include coal-fired plants – in an attempt to win over wavering colleagues.

This is in line with one of 56 Australian Competition and Consumer Commission recommendations to cut power prices.

Labor leader Bill Shorten earlier told a caucus meeting the Prime Minister had surrendered to climate sceptics in his government.

“The only thing guaranteed to come out of today is higher power prices and less renewable energy. We have cobbled together today a Frankenstein’s monster of a policy,” he said.

Crossbench conservative senator Cory Bernardi believes the policy will push up prices.

“Unless they remove the barriers to nuclear power … and until they walk away from the Paris Agreement, they won’t have my vote,” the former Liberal senator told Sky News.

Trade Minister Steve Ciobo said abandoning the Paris deal would torpedo Australia’s chances of a free trade deal with the European Union, negotiations for which are underway.

-With AAP