Deputy Prime Minister Barnaby Joyce has compared the New South Wales Independent Commission Again Corruption (ICAC) to the Spanish Inquisition, three years after a similar body was proposed by the federal government. 

Gladys Berejiklian resigned as NSW Premier on Friday after the state's corruption watchdog revealed it was investigating claims she breached public trust when awarding grants to several community organisations. 

Ms Berejiklian has not been charged, but said she had no option but to resign as premier given ICAC would hold public hearings later this month to investigate any potential conflicts of interest. 

The federal opposition is again renewing calls to establish a federal anti-corruption body, but Mr Joyce today criticised the basic function of the NSW integrity commission.

"The process of ICAC is lauded by people who want greater power for minority groups against the wishes of the majority, that's how I see it," Mr Joyce told Channel Seven. 

"This is not the great sort of righteous process – it's a little bit like the Spanish Inquisition. 

Geoffrey Watson SC, director of the Centre For Public Integrity and a former counsel assisting the NSW ICAC, said the corruption watchdog performed a crucial role outside of the legal system.

"The thing is that ICAC was introduced because of a special need, which is a special need because of the nature of corruption in the public sector," he said.

"You need a specialist body with specialist powers.

"ICAC is actually operating as a ... standing royal commission in these sorts of affairs."

Prime Minister Scott Morrison first proposed a federal anti-corruption commission in late 2018, but no legislation has been introduced and legal experts criticised the initial proposal as "having no teeth". 

Former attorney-general Christian Porter initially outlined plans for the commission to have two separate divisions – a law enforcement division with public hearings, and a government division that would have private hearings. 

A spokesman for Attorney-General Michaelia Cash said the government intended to introduce legislation by the end of the year, and 47 consultation sessions had been held with legal experts and civil society groups. 

Federal body should learn from NSW, Labor says

In light of Ms Berejiklian's resignation, senior Labor figures have acknowledged any national watchdog would need to do a better job at protecting the reputation of witnesses, including potentially making early hearings private.

Shadow Attorney-General Mark Dreyfus has been one of the loudest voices for a federal anti-corruption body, recently noting it had been three years since a commission was first proposed. 

Mr Dreyfus said any national body should not copy state-based arrangements without improvements. 

"Innocent people, who were simply assisting the commission with a particular inquiry, were the subject of smears and completely unwarranted adverse criticism," Mr Dreyfus told AM.

"I think you could write something into the legislation which helps guard against that feature."

Independent MP Helen Haines, who recently put forward her own bill, said the NSW model should not be copied. 

"It's then up to the commissioners to determine. That makes it a little different to the NSW model."

But she pointed out the events in NSW last week highlighted the need for some kind of anti-corruption body at a federal level.

"What's transpired in New South Wales over the past few days has demonstrated, yet again, the glaring gap in our federal parliament that there is no integrity commission, that any such allegations of corruption can never be dealt with," she said.

That is something NSW ministers have been calling for in recent months, but former ICAC assistant commissioner Anthony Whealy has told The Australian that reverting to completely private sessions would be taking the state "back to the dark old days".