A group of high-profile judges have called for a proposed federal anti-corruption body to be given the powers of a royal commission, warning “an ineffective commission is worse than no commission at all”.

The Coalition released its preferred model for a national integrity commission late last year but the body was quickly criticised for a lack of public hearings, below-par resourcing, its selective treatment of politicians and the high threshold of criminal suspicion required to commence an investigation.

The six judges, some of whom have served as state anti-corruption commissioners, said the body could only be truly independent if it was led by commissioners with a strong enough “quality and reputation” to withstand the types of pressure they would inevitably face.

They said commissioners must be on secure but limited fixed-term contracts, with no prospect of reappointment. Commissioners’ pay should not be reduced following their appointment and they must be “guaranteed sufficient funding, and adequately experienced and skilled staff” to function effectively.

The judges said it was also “crucial” the commission be given the power to hold public hearings when it was deemed in the “public interest”, and handed a broad enough remit to target “all forms of serious or systemic corruption within or affecting any element of the public sector, including the parliament, the executive and the judiciary”.

“The commission we envisage would fill a serious gap in Australia’s capacity to minimise corruption,” the judges said in a submission to an inquiry considering a model proposed by the crossbench. “It would investigate with rigour and fairness, and expose without fear or favour, behaviour that deliberately impairs, or could impair, the honesty, impartiality or efficacy of official conduct wherever it occurs in the federal sphere. The case for such a commission is compelling, and much of our advocacy has been focused accordingly.”

The group of five judges, who form the Australia Institute’s integrity committee, include New South Wales supreme court judge Anthony Whealy, the former NSW Independent Commission Against Crruption commissioner David Ipp, and retired senior judges Stephen Charles, David Harper and Paul Stein.

The judges said the commission must be free to investigate any corruption it deemed serious or systemic. It must have the power to initiate its own investigations, make arrests, gather and hold evidence, and conduct searches, they said.

“The commission must be granted the investigative powers of a royal commission to undertake its work, to be executed at the discretion of the commissioner.”

Public hearings, they said, should be held if the commission determined it was in the public interest.

“It is now generally accepted that it is difficult to uncover corruption without the aid of public hearings,” the judges said. “Of course public hearings should be held sparingly and only where they are demanded by the public interest.”

The judges argued the governor general should have a role in selecting the chief commissioner and deputy commissioners.

The Coalition’s proposal currently prohibits the commission from making findings of corrupt conduct. It would only be able to refer cases to prosecutors to take through the courts. The judges offered some support for the position, saying they believed the commission “must have the power to make findings of fact, but should not have the power to make corrupt conduct findings”.