Experts and independent MPs are warning the bar has been set "too high" under the government's model, which was introduced to the lower house on Wednesday morning.

But the opposition has argued it believes the proposal is balanced to stop it becoming "an endless witch-hunt" or a show trial.

The bill will now be scrutinised by a parliamentary committee over the next six weeks, allowing parties to make submissions and appear at public hearings.

Attorney-General Mark Dreyfus outlined hearings could be publicly held under "exceptional circumstances" but that the default position would to be hold them in private.

"The legislation provides guidance to the commission on factors that may be relevant to determining the public interest in holding a public hearing," Mr Dreyfus said.

"These factors include any unfair prejudice to a person's reputation, privacy, safety or wellbeing if the hearing were to be held in public.

"These factors also include the benefit of making the public aware of corruption."

But critics are worried the changes suggest Labor is watering down its pre-election promise to deliver a transparent integrity body.

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Retired judges, Stephen Charles and Michael Barker, joined prominent anti-corruption lawyer Geoffrey Watson at Parliament to warn against the inclusion of the "exceptional circumstances" provision.

They argued it would give those being put before the federal body a chance to challenge its definition in the High Court, causing unnecessary delays and costs to corruption investigations.

"There is no such [single definition] because one person's idea about what is exceptional is unexceptional to another person," Mr Watson said.

"How long is a piece of string? Well, it's about the same length as an exceptional circumstance."

Transparency International Australia chief executive Clancy Moore added he was concerned the specific wording could result in many hearings being held in secret.

"We are concerned the bar on public hearings is set too high," he said.

"Public hearings are essential for detecting and preventing corruption. The risk that some important examples of corruption will be dealt behind closed doors and in secrecy is a blow for transparency."

Independent MPs and senators repeated their concerns over the public hearing threshold on Wednesday morning, vowing to use the next six weeks to fight for it to be lowered.

"Public hearings are clearly something that we're going to have to look at and continue to push hard for - it shouldn't be [under] exceptional circumstances," ACT senator David Pocock said.

"We're setting up an independent commission - they should have the independence to actually decide what is in the public interest."

Tasmanian senator Jacqui Lambie said Australians expected people who have done something wrong to be held accountable.

"There's no public trust in politicians out there and if you want to play this out, it's going to have to be in the public arena," she said.

"[The private hearing default] is just about going to kill off the trust that we're trying to establish with the Australian people. You have to open this up.

"Besides that, the Attorney-General said all these decisions he was going to leave up to the commission itself, so why are we now starting to dictate who will be behind closed doors and who isn't? It's not on."

But Opposition Leader Peter Dutton warned a sensible approach toward public hearings was needed to ensure the body didn't become "an endless witch-hunt".

He flagged he was worried if the Greens and crossbenchers pushed for amendments to lower that threshold, peoples' careers and reputations would be at risk.

"I want people who have committed a crime to go to jail. That's what I want," Mr Dutton said.

"I don't want a situation where somebody has their reputation trashed and after a couple of years don't even know whether or not the investigation is still standing.

"We have seen circumstances where investigations have come to a conclusion and the person under investigation hasn't even been advised that they've been cleared."