When a member of the government professes concern for the independence of an ABC journalist, it may be taken as fair evidence they are grasping at straws.

It wasn’t just any journalist Attorney-General Christian Porter was defending this week, either. It was Andrew Probyn, whose on-air characterisation of Tony Abbott as “the most destructive politician of his generation” a few months back inspired furious complaint from the government. Infamously, it also led to a demand from then ABC chairman Justin Milne that Probyn be “shot” because the journalist threatened the broadcaster’s chances of getting more funding from a government that hated him.

But on Monday, Porter was suddenly solicitous of Probyn’s independence. It was an attempt to undermine the establishment of a powerful new anti-corruption body, the national integrity commission, which has the support of Labor, the Greens, most of the newly powerful parliamentary crossbench, a large cohort of the nation’s most eminent lawyers, civil society groups and, overwhelmingly, the public.

“The fact is that Mr Porter has made a basically unfounded, reckless and incorrect statement and has misled parliament.”

The proposed legislation, introduced on Monday morning by independent MP Cathy McGowan, was “excessive” and “dangerous”, Porter said, because it included “an incredibly broad and low definition of corruption” that could see “hundreds of thousands of civil servants would potentially be declared corrupt for the most minor matters”.

That would include journalists working for the ABC and SBS, who are technically public servants. And Probyn, who had been found by the Australian Communications and Media Authority to have breached ABC standards of impartiality in his assessment of Abbott, would therefore fall foul of the new commission.

“No ifs, ands or buts,” Porter told the house, “Andrew Probyn would be found to have committed corruption.”

His assertion set off laughter in the chamber, but Porter insisted: “Read the bill.”

David Ipp, AO, QC, wasn’t laughing. The former commissioner with the New South Wales Independent Commission Against Corruption (ICAC) had not only read the bill, he was one of the eminent legal minds who had informed its drafting.

After consulting with others, Ipp released a written response on Tuesday, effectively accusing Porter of lying.

The claim that public servants who made innocent mistakes, or were guilty of minor misconduct, such as that involving Probyn, would be targeted by the new watchdog was “patently absurd”, according to Ipp.

“These statements by the Attorney-General … are false and are not borne out by the wording of the bill,” he wrote.

Ipp went on to quote the relevant section of the bill, which specified the limits of behaviour that might be deemed corrupt – a criminal or disciplinary offence, reasonable grounds for dismissal or a breach of an applicable code of conduct.

The suggestion that Probyn might be caught by the legislation, Ipp said, “is simply nonsense”.

“The fact is that Mr Porter has made a basically unfounded, reckless and incorrect statement and has misled parliament.”

Other legal heavyweights piled on, too, including Anthony Whealy, QC, the former chair of the Australian chapter of the global anti-corruption organisation Transparency International and, like Ipp, a former judge with the NSW Supreme Court of Appeal. Whealy also accused Porter of misrepresenting the proposed legislation.

He conceded the bill – which runs to more than 250 pages – is complex, but he said the definition of corruption “was based on that in the NSW ICAC legislation’s definition of corruption, which worked very well”.

“We haven’t seen any journalist sent to jail for their reporting in NSW,” said Whealy, who, along with Ipp and several other senior former judges, has worked on design principles for the new commission for a year through a group called the national integrity committee. This committee falls under the umbrella of the progressive think tank The Australia Institute.

“In layman’s language,” Whealy told The Saturday Paper, “what Christian Porter points to is qualified by a limiting clause that says it isn’t corrupt conduct unless it amounts to a criminal offence or other serious thing. He’s just ignored that qualification, that very serious limitation.”

There are further safeguards, too, which Porter must have noticed in reading the bill – provisions that would knock out frivolous or vexatious cases and limit investigations to serious and systemic matters.

That is not to say there isn’t room for improvement. All of the parties who had input into the bill acknowledge that – that is, Cathy McGowan and her office who undertook the Homeric task of drafting, the lawyers who worked through The Australia Institute, and Transparency International Australia’s non-executive director A. J. Brown, a professor of public policy and law at Griffith University, who has worked towards such legislation for almost 15 years.

Says Brown: “Of all the possible options, from minimalist to comprehensive, Cathy McGowan and the crossbenchers decided to put legislation around the comprehensive option.

“They have set a high standard and a broad definition. But, better to start broad rather than narrow and then find in five years’ time we have gaps in the system still. This is where the serious debate and analysis begins.”

McGowan’s proposal is not particularly radical. The definition of corruption was modelled on Australia’s most effective state body, ICAC in NSW. And as McGowan said in introducing the legislation, the investigative functions of the commission largely mirror those of an existing body, the Australian Commission for Law Enforcement Integrity, known as ACLEI. Few Australians would have ever heard of ACLEI – its range is narrow and it has never held public hearings.

“This is a tried-and-tested approach at the Commonwealth level, and this bill incorporates best practice from the integrity framework of other jurisdictions. We’ve learnt our lesson; it’s not a cut-and-paste of the state-based integrity commission,” McGowan said.

But it would be powerful: effectively a standing royal commission, able to hold public hearings and conduct retrospective investigations. Tasmanian independent Andrew Wilkie, who also had input into the package, suggested that was the real reason the government was dead set against it.

Wilkie enumerated several examples of dubious government decisions – $30 million given to Murdoch’s Foxtel “for reasons that are still unexplained”, the grant, without any due process of nearly half a billion dollars to the private Great Barrier Reef Foundation, the circumstances surrounding Australian spying on East Timor during negotiations over oil and gas resources.

“Perhaps in all of those cases there was no misconduct and they were all good decisions by good people,” Wilkie told the house of representatives. “But we don’t know, because we don’t have any means to examine those sorts of issues.”

“Why,” he asked, “is the current government so anti some sort of federal anti-corruption or integrity authority? If the government has nothing to hide, it will have nothing to fear from the establishment of such an organisation.”

In his speech, Porter suggested the innocent did have reason to fear such a body, and criticised the state-based anti-corruption commissions, such as ICAC, for allegedly having ruined lives and careers on the basis of “no good fact and no good process”.

Particularly in relation to NSW, it is a tired and unjustified claim, repeatedly made by right-wing politicians, reactionary elements in the media, particularly the Murdoch press, and the corrupt themselves, according to Whealy and Ipp.

Says Whealy: “There’s been a great fuss in the Murdoch press about ICAC, and people have been put forward as innocent. They are usually rather corpulent, rich businessmen who’ve been found corrupt in NSW. They have taken their cases to the Supreme Court, and the court has chucked them out as having no grounds for complaint. I note Eddie Obeid failed again in the High Court only last week.”

Ipp notes that after 11 NSW and federal Liberal Party politicians fell foul of an ICAC investigation into breaches of election funding laws in 2014, the state government responded by cutting its funding, reducing its powers, making it more difficult to hold public hearings.

It was not just the conservative parties who feared being caught, of course. The truth is that both major political parties long resisted any move towards a national anti-corruption body. That changed in January this year, though, largely due to the efforts of Labor’s shadow attorney-general, Mark Dreyfus.

It represented an overdue recognition that “the NIC was, first, an intrinsically good idea and, second, a politically good idea”, says Whealy.

And long overdue, for public opinion was by then well out in front of politics. Some three-quarters of the people wanted a federal anti-corruption body, as did a considerable weight of legal opinion. Two months before Labor committed to establishing a commission, 34 former judges, including a former chief justice of the High Court, had written an open letter calling for one.

As is so often the case with the adoption of progressive reform, the Greens were the first to propose one, in a bill put by then leader Bob Brown in 2010.

Introducing her bill on Monday, McGowan paid due respect to the Greens’ repeated efforts since, as well as the work by the Australian Research Council, Transparency International, The Australia Institute’s national integrity committee, and others, including her crossbench colleagues.

Fellow crossbencher Rebekha Sharkie said: “If you are not going to listen to us, if you are not going to listen to the crossbench, if you’re not going to listen to the Australian people, for goodness sake, why don’t you at least listen to 34 eminent former High Court and Federal Court justices?”

But Christian Porter made it clear he was not listening. On ABC Radio on Tuesday, he dismissed their NIG proposal as unworkable. He also revealed that before the sacking of Malcolm Turnbull he had been working on a proposal of his own. Exactly what he envisioned was left unclear.

“The public line is that it is now subject to a cabinet proposal, but we have no sense of what it is beyond the claim that it could be a standalone integrity commission or more resourcing for ACLEI and improving its co-ordination with other agencies,” says Fiona McLeod, SC, the chair of Transparency International Australia. “Our strong view is that tinkering with ACLEI is not going to provide the coordinated approach and integrity framework that we need. It is not adequately resourced or supported.”

Her scepticism would seem well founded, for Porter’s comments suggest the government has no intention of supporting any commission with real teeth. In parliament, Prime Minister Scott Morrison dismissed the whole idea as a “fringe issue”.

Proponents of the integrity commission suggest the government’s approach to corruption is akin to its approach to climate change: an attempt to placate public concern through the appearance of action, while not taking any meaningful action. As the venerable political commentator Michelle Grattan wrote on The Conversation website on Monday: “The government’s preference would be to do nothing. But that’s no longer politically viable.”

On Monday, Cathy McGowan will introduce a second part of her reform package, which deals specifically with integrity standards and a code of conduct for politicians.

It will be interesting to see what reason Porter comes up with, this time, to dismiss it.