Queensland's commission of inquiry into organised crime is probing allegations police failed to investigate hundreds of complaints from across Australia of serious investment fraud allegedly carried out by companies based on the Gold Coast.

The ABC has learned the commission has summoned witnesses, including at least one victim of the frauds, to testify at secret hearings held in Brisbane over the past two weeks.

A lawyer acting for the Queensland Police Service (QPS) cross-examined the witnesses at the hearings.

The witnesses include people who have featured in a series of ABC reports exposing fraudulent cold-calling investment schemes, often involving sports betting, run out of high-pressure sales offices — so-called "boiler-rooms" — on the Gold Coast.

The ABC reported last month the inquiry had asked private investigator and cybercrime expert Ken Gamble to make a detailed submission on his knowledge of the boiler rooms and his dealings with Queensland Police.

Mr Gamble told 7.30 in May the QPS fraud squad had repeatedly failed to act on evidence he had provided of major investment fraud, including an alleged multi-million dollar scam involving cartoonist Larry Pickering.

Mr Pickering has denied involvement.

Do you know more about this story? Email investigations@abc.net.au

The commission of inquiry's investigation comes after Queensland's Crime and Corruption Commission told the ABC earlier this year it was investigating the possible involvement of corrupt former police in protecting Gold Coast fraudsters.

The inquiry, chaired by former deputy director of public prosecutions Michael Byrne QC, was set up in February by the incoming Palaszczuk Labor Government.

Due to report in October, it was part of a suite of measures to help form the administration's response to controversy over the former Newman government's controversial anti-bikie laws.

It has broad terms of reference, including investigating "key enablers" of organised crime, such as money laundering and cybercrime, and "the relationship between organised crime and corruption in Queensland".

It will also look at the "adequacy and appropriateness of the current responses of Queensland law enforcement".

The QPS declined to answer detailed questions about a range of scams that have been the subject of complaints to police, saying resources were directed "where the threat is highest".

The QPS fraud squad has undergone a shake-up in recent weeks, with the long-serving head of the unit, Detective Superintendent Brian Hay, taking a 12-month career break amid an internal probe into alleged misuse of a corporate credit card.

The QPS said last month it had found "no evidence of impropriety" but the investigation was ongoing.