Clashing with Kevin Rudd on the ABCs Q&A program on Monday night, Mr Turnbull said the same could not be said of Mr Rudd and the Labor cabinet.

Mr Rudd and Mr Turnbull, both preferred by voters as leaders of their respective parties, squared off on national television over issues ranging from tax reform to industrial relations.

Mr Turnbull said he would not be the Liberal Party leader and "certainly not the next Liberal prime minister", but voters could be assured he would be at the cabinet table and part of the decision-making process.

But the same could not be said of Labor, he said, because Mr Rudd would be on the back bench if Labor were re-elected.

Mr Rudd said leadership had many forms. He said Mr Turnbull and Tony Abbott were chalk and cheese and Mr Turnbull would be more at home in Labor.

Mr Turnbull shot back, saying Mr Rudd was in the same party as Eddie Obeid, whom Mr Rudd swiftly condemned. Mr Rudd said the Independent Commission Against Corruption hearings were important to Labor regaining its integrity.

He dismissed a question suggesting he would be Labor leader again but decried the Balkanisation of politics, saying it had become "a rolling Punch and Judy show" and mature debate had become impossible.

"It suffocates effective discussion,' he said.

Labor could win the next election, and Labor's greatest asset was Mr Abbott, he said.

Mr Turnbull backed industry calls for changes to the industrial relations system but conceded the strength of the 2007 campaign against WorkChoices meant the Coalition had to tread lightly.

"There is no question we overreached with WorkChoices," he said, adding the Coalition now "needed to bring the community with it" and promise just incremental change.

Mr Rudd said the electorate simply did not trust the Coalition on industrial relations.

He chided Mr Turnbull for belonging to a political party that twice voted against a price on carbon and said he had not changed his view "one bit" on climate change policy after Mr Turnbull found himself defending the Coalition's direct action policy, which he had previously criticised.

Mr Rudd said China was moving to a national price on carbon and Tony Abbott would be "the last of the Mohicans".

Mr Rudd defended the original mining tax, which was conceived under his leadership, saying it was designed to tax super profits and help ease the pressure on the non-mining sector caused by the high dollar.

Mr Turnbull said this was " a really bad idea" and the government should have cut spending to allow the Reserve Bank to cut interest rates.

The renegotiated minerals resources rent tax has made no or little revenue in its first three months but Mr Rudd, who opposed the watering down of the tax after he lost the Labor leadership, defended it.

"Three-quarters of the year remains, and let's see what the full year generates," he said.

Commodity prices had "come off by about a third" since he announced he original resources super profits tax, he said.

When asked how to find the $6.5billion needed annually to fund the proposed Gonski education reforms, both said no new taxes should be levied. Mr Rudd said economic growth was the key to finding the money while Mr Turnbull said more efficient use of current tax revenue was needed.

The Reserve Bank board member and former chief executive of the Australian Industry Group, Heather Ridout, said robust tax reform was needed, which included a need to look at the rate and base of the GST.

Ms Ridout was a member of the Henry tax review, which was commissioned by Mr Rudd but was not allowed to look at the GST.

Mr Rudd said the GST ultimately was a regressive tax that hurt poorer people more, and internet sales would erode the tax takings over time.