Barnaby Joyce has floated the idea of breaking up the banks following revelations of misconduct at the royal commission – which the former deputy PM now admits he was “wrong” to oppose.

In comments that inevitably reflect on the fierce opposition of Malcolm Turnbull, Scott Morrison and Kelly O’Dwyer to the inquiry, Mr Joyce said in a tweet that what he had heard so far was “beyond disturbing”.

But going further, the former Nationals leader said the government should consider whether banks should be involved at all in financial planning.

“The banks appear to have blatantly taken the support of government as the reason they can do what they like,” he said in a statement

They should consider whether they should be in the financial planning business after the evidence delivered. It appears from evidence to be too much of a conflict of interest and a temptation for them.”

The commission heard this week that AMP had charged thousands of dollars customers for products they had never received – and then deceived corporate regulator ASIC about its conduct.

Mr Joyce’s comments come as the Turnbull government confirms it will allow more than the 12 months originally set aside for the inquiry if requested by Commissioner Kenneth Hayne.

The government argued it was right to expand the commission but have been reluctant to admit they were wrong in opposing the commission.

Mr Joyce apologised for “being so naive to have swallowed their line of ‘we are good corporate citizens’”.

“Maybe they should now as well,” he said.

His Nationals colleague David Gillespie also said there was “a lot of validity” to the idea the banks should not also operate in the financial planning business.

Mr Morrison said on Tuesday the instances of misconduct revealed by the commission were “very serious issues” that “can carry gaol sentences”.

He said he was “deeply disturbed by it”.

The Turnbull government established the commission in November last year after a group of Nationals, led by senators John ‘Wacka’ Williams and Barry O’Sullivan, threatened to establish an inquiry via Parliament.

Supporters of the commission attacked the government on Thursday for having opposed it for so long.

“The cavalcade of Coalition Ministers and MPs commenting about the revelations coming from the banking Royal Commission is breathtaking in its hypocrisy,” Labor’s shadow finance spokesman Jim Chalmers said.

Mr Morrison described the decision at the time as “regrettable”, but said it was “necessary” because the political uncertainty was causing damage.

Addressing the National Press Club on Thursday, Acting Prime Minister Michael McCormack said he was glad the government had been pressured into holding the commission by his Nationals colleagues.