Former Victorian Supreme Court of Appeal judge Stephen Charles and former NSW Supreme Court of Appeal judge Anthony Whealy joined MPs including Helen Haines, Andrew Wilkie, Rex Patrick, Rebekha Sharkie, Mark Dreyfus, Zali Steggall, Jacqui Lambie, Bob Katter and Pauline Hanson to criticise the government's model of anti-corruption watchdog. Mr Whealy said the watchdog as proposed would be "completely ineffective" as it would only allow politicians and public servants to be investigated if there was a reasonable suspicion of a criminal offence.

"To have two divisions in an integrity system is totally counterproductive to the effective exposure of corruption. It should be, of course, one rule for all. Once you start to carve out people who are not subject to the rules of an anti-corruption body, you have failed at the outset," Mr Whealy said.

"I would refer to the fact that you can have a public hearing involving a policeman or a border enforcement officer, but you can't have a public hearing for a politician or the majority of public servants.

"Why? Is that fair? Would the community accept that? And you can't have public findings of fact involving corruption by politicians and the majority of public servants. But you can about law enforcement officers and so on. That all harks back to my preliminary point. It has to be one system for all, otherwise, it won't work."

Troy Roberts from the Australian Federal Police Association questioned why police were subject to a lower bar than politicians and public servants.

"It should be the same rules for everybody," Mr Roberts said.

Labor's attorney-general spokesman Mark Dreyfus said the proposed model was "flawed and compromised".

"What [the government] wants is a cover-up commission, a commission that will never investigate ministers, a commission that will never investigate members of parliament," Mr Dreyfus said.

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Greens Senate leader Larissa Waters said the commission as it stood would "actually perpetuate and cover up corrupt conduct".

"If we have a sham corruption watchdog that is a protection racket for politicians, that is worse than not having one," Senator Waters said.

The Senate is poised to reject the proposal if key changes are not made between now and March.

Tasmanian independent Andrew Wilkie urged Coalition MPs to "put the public interest ahead of your party" and be prepared to cross the floor over the issue.

"I'm hard pressed to think of a more important issue, and one that would warrant at least a couple of members of the government crossing the floor," Mr Wilkie said.

Queensland MP Bob Katter pointed out the only reason a banking inquiry got up was because George Christensen crossed the floor.

"He had the courage of his convictions to stand up," Mr Katter said.