The outgoing head of the Department of Prime Minister and Cabinet says power prices would be lower now if an emissions trading scheme had been implemented over a decade ago.

"Whatever else you do, Renewable Energy Target, or anything else, they can be no cheaper than putting an explicit price on carbon," Martin Parkinson told 7.30.

"The difference is where's the cost in an emissions trading scheme (ETS)? The cost is quite visible. It's there, it's the price of the permit.

"In the case of the Renewable Energy Target or any other intervention, then often that price is hidden from the view of the consumer. But ultimately the consumer's paying because it's built into the price of power.

"At the moment what we've got is a lot of burden falling on energy prices.

"If we had an ETS it would have smeared that cost across all parts of the economy."

'We could have done it cheaper'

Martin Parkinson worked under a number of prime ministers and first started looking at an ETS during the Howard government. ( ABC News )

Dr Parkinson first began looking at an emissions trading scheme in 2007, in the final year of the Howard government.

"When I think back to where we were in 2007, when we first started thinking about this for Prime Minister Howard, we had in mind technology falling in price terms over the period ahead," he said.

"What's actually happened is that [the price of] technology has fallen, but it has fallen dramatically more quickly, dramatically more sharply than anybody anticipated at the time.

"The point of a price mechanism is that's how you actually accelerate the uptake of the technology."

Dr Parkinson said if Labor's proposed Carbon Pollution Reduction Scheme (CPRS) had been introduced in 2009 it would have been successful in delivering lower power prices.

"We could have achieved what we were trying to achieve — we could have done it in a way that was cheaper," he said.

"Now, there is a price. It can either be explicit or implicit. And at the moment it's implicit, and where do you see that price? You see it in the price of electricity and gas.

"And until we have a sensible set of policies that can be sustained in the long run, then we will have prices above what we need to have."

Parkinson rejects criticism of former ministers taking new jobs

Dr Parkinson found neither Christopher Pyne nor Julie Bishop breached ministerial standards by taking jobs in the private sector. ( ABC News: Marco Catalano, AAP: Mick Tsikas )

One of Dr Parkinson's last tasks was to review whether former ministers, Julie Bishop and Christopher Pyne, had breached any rules in taking jobs soon after leaving Parliament.

He found that neither had done anything wrong.

"Some of these people who are critical of former ministers are really implicitly saying ministers should never be allowed to hold a job again," Dr Parkinson said.

He said that was an unrealistic expectation.

"No PM [could] ever work again because they cover so many issues, no treasurer could ever work again because they're involved in so many issues," he said.

"The key issue is to ensure that people don't misuse information that they obtain purely because they happen to be minister for X at particular point in time."

Parkinson 'never actually formally sacked'

Martin Parkinson was one of several departmental secretaries sacked by Tony Abbott. ( ABC News )

After working for prime ministers going back to Mr Howard, Dr Parkinson did not have a pleasant time under Tony Abbott's stewardship.

He was one of several departmental secretaries sacked by Mr Abbott.

The widespread view at the time was that Dr Parkinson was being punished for his association with Labor's climate change policies.

Mr Abbott's treasurer, Joe Hockey, made it clear he wanted Dr Parkinson to stay in the job.

Having been told his services would no longer be required, Mr Abbott was subsequently forced to personally ring Dr Parkinson to ask him to stay on until after Australia hosted the G20 meeting in Brisbane in 2014.

Dr Parkinson insisted he "was never actually formally sacked" because of that request that he stay on.

"I left at the end of 2014, 15 months after I was told that my services were not wanted," he said.

Dr Parkinson was then rehired by Malcolm Turnbull in 2015 but said his earlier departure sent a very bad message to the public service.

"Whether it was intended or not, people interpreted it as you shouldn't take on roles that could be perceived as controversial," he said.

"Even when all you're doing is actually carrying out the lawful instructions of an elected government."

But he has backed Scott Morrison's recently announced plans to increase accountability in the public service.

"He has a very clear focus on wanting to achieve the delivery of a whole range of his priorities through this term," he said.

"And he wants clearly measurable and reportable metrics. So I personally think it's a very good initiative."