Electricity from new coal-fired power plants would cost twice as much as power from existing coal power stations, Treasurer Scott Morrison has warned.

However, former prime minister Tony Abbott said Mr Morrison made more sense when he brandished a lump of coal in Question Time last year.

A group of Coalition MPs calling itself the Monash Forum has been circulating a letter calling on the Government to consider building a new coal-fired power station.

But on Wednesday, Mr Morrison slammed that push, saying coal from existing plants could be sold into the energy grid for between $30 and $40 each MegaWatt hour.

"There is a difference between old coal and new coal," he said.

He said it was cheaper because the old power plants had already been written off by their owners.

Mr Morrison said new high-efficiency low-emissions (HELE) coal generation plants would sell power for between $70 and $80 each MegaWatt hour — or at least twice as much as the old power stations.

"You don't just open up one down the road and all of a sudden it is producing power at the same price as Bayswater or any of the others — that is just not an economic fact," Mr Morrison said as he hit back at the Monash group.

In response, Mr Abbott argued on Sydney Radio 2GB new coal plants still produced cheaper power than new gas plants, and he said they were more reliable than renewables.

Tony Abbott said Scott Morrison made more sense when he brandished a lump of coal in Question Time. ( ABC News: Nick Haggarty )

Coal phobia 'politically contagious', Abbott says

Mr Abbott called Mr Morrison's response puzzling.

"Scott Morrison himself came into Question Time one day a few months ago and waved around a big lump of coal and said to the Labor Party: 'This is coal, this is a good thing, don't have coal phobia'," he said.

"I thought he was making a lot more sense that day than he was today."

He noted having a phobia about coal seemed to be politically contagious.

Former deputy prime minister Barnaby Joyce has also dismissed Mr Morrison's warning energy from new coal power plants would be much more expensive to deliver.

"If that was the case, then we wouldn't build the Harbour Bridge, we wouldn't build any tunnels. Let's just stop still. Let's stop civilisation where it is," he told 7.30.

The group of conservative politicians pushing the Government to invest in new coal-fired power stations includes former ministers Kevin Andrews, Eric Abetz and Mr Abbott.

It chose the name "Monash Forum" because World War I General Sir John Monash was involved in developing a brown coal-fired power industry in Victoria.

The "Monash Forum" includes Tony Abbott (left) and Kevin Andrews (right), as well as Eric Abetz. ( ABC News: Matt Roberts )

But General Monash's descendants have asked the MPs stop using that name.

"It has come to our attention that a group of conservative politicians have formed themselves into a lobby group for coal," they said in a statement.

They said they were direct descendants of the General and "at the very least it was discourteous to use it without informing us".

"More than that, we disassociate ourselves specifically from the forum's use of the Monash name to give their anti-science and anti-intellectual argument an air of authority and we ask that they withdraw the name," the statement said.

The family members said Sir John was no left-wing radical — he was "intellectual and scientific".

They said he developed coal for power generation when it was the leading technology, but they are sure today "he would be a proponent of the new technologies, [for example] wind and solar generation rather than revert to the horse and buggy era".

The RSL has also criticised the use of the military hero's name by a political group.