Malcolm Turnbull has warned against the “idiocy” of a fresh internal brawl in the federal coalition over coal-fired power, saying it’s damaging the NSW conservative government’s chances of re-election.

The former Liberal prime minister said infighting over energy as well as leadership tensions in the Nationals were hurting NSW Premier Gladys Berejiklian’s hopes of winning next week’s vote.

“You haven’t worked out how damaging it is? Clearly, all of the distraction from the feds is unhelpful. That’s obvious,” he told The Sydney Morning Herald and The Age on Friday.

Divisions in the Morrison government have re-emerged in the past week, with pro-coal MPs pushing for the federal government to fund a new power station in Queensland.

The issue has also fuelled doubts over Nationals leader Michael McCormack’s leadership after Barnaby Joyce hinted at a possible challenge before retreating.

Mr Turnbull said new coal-fired power generation in Australia would not come cheap.

“The cheapest form of new energy in Australia, if you’re talking about dispatchable power, is a combination of renewable power, wind and solar, with zero marginal cost generation, plus storage,” he said.

“We have the means to get to zero emission or near zero emission in Australia but you need to plan it.

“You’ve got to have engineering and economics rather than ideology and idiocy and, regrettably, there’s quite a lot of that around.”

Polls indicate the coalition and Labor are neck and neck ahead of the March 23 state election.

Asked about Mr Turnbull’s comments, Finance Minister Mathias Cormann told Sky News: “It’s good to see Malcolm help to win the election in New South Wales.”

Senator Cormann dismissed rumours he could depart politics if the Morrison government wasn’t re-elected at the federal poll in May.

“I’m very bemused by all of these reports. I am absolutely in it for the long haul,” he said.

“The Labor party might want to see the back of me but no such luck. Wishful thinking by the Labor Party.”

Speculation is also rife Mr Turnbull’s ally and federal Liberal MP Craig Laundy will announce his retirement from politics.

“Craig is a good friend of mine and I talk to him regularly. But in terms of those sort of decisions, he’ll make them himself,” Mr Turnbull said.