Almost two years after Tony Abbott vowed to "shine a great big spotlight into the dark corners of our community to ensure that honest workers and honest businesses get a fair go", the findings of the Royal Commission into Trade Union Governance and Corruption are to be released by the Federal Government.

Key points: Government set to release findings from trade union royal commission

Government set to release findings from trade union royal commission The commission sat for 189 days and heard evidence from 525 witnesses

The commission sat for 189 days and heard evidence from 525 witnesses High-profile witnesses included Julia Gillard and Bill Shorten

The former prime minister then urged "people to come forward and tell their stories".

"We want the culture of cover-up and corruption to be ended for all time," he said as he announced the royal commission in February 2014.

To his critics, it was seen as an escalation of an attack on Opposition Leader Bill Shorten, the former national secretary of the Australian Workers Union (AWU), and a test of Mr Shorten's resolve to tackle allegations of corruption within the union movement.

The terms of reference focused on governance and financial accountability.

There were claims of trade union slush funds, rorting and misuse of union funding.

The royal commission was as controversial as it was colourful with the ACTU describing it as a "$100 million waste of taxpayers' money".

The royal commissioner, Dyson Heydon QC, a retired High Court judge, sought to reassure the union movement.

"The terms of reference rest on certain assumptions which are not hostile to trade unions," Justice Heydon said on the opening day of the commission.

"The terms of reference do not assume that it is desirable to abolish trade unions. They do not assume that it is desirable to curb their role to the point of insignificance."

Liberal senator Eric Abetz said the commission's findings would leave little doubt about how unions operated and reinforce the need for change.

"The evidence is there, it's undisputed, it rolled out day after day after day," he said.

"Nobody can now sit back and say there's not sufficient evidence to reinstitute the Australian Building and Construction Commission, or to institute a registered organisations commission."

Demands for Heydon to step aside

But Justice Heydon was pressured to step aside after it was revealed he had accepted an invitation to deliver the Sir Garfield Barwick speech at a Liberal Party fundraiser.

Seven unions said it amounted to a perception of "apprehended bias".

The royal commissioner did not disqualify himself and dismissed the application.

That drew criticism it left the inquiry "politically tainted".

The royal commission sat for 189 days and heard evidence from 525 witnesses in public and private hearings.

There were 75 case studies. High-profile witnesses included former prime minister Julia Gillard and Mr Shorten.

Each faced forensic examination, but counsel assisting the commission has not recommended any findings of wrongdoing.

Ms Gillard gave evidence for four hours about her time as a solicitor, 20 years ago at Slater and Gordon.

She faced questioning about the establishment of an AWU slush fund and her dealings with her then boyfriend and union official, Bruce Wilson.

The counsel assisting the royal commission Jeremy Stoljar SC said "she did not commit any crime and was not aware of any criminality on the part of these union officials".

But he went on to say that "aspects of her professional conduct as a solicitor appear to be questionable".

Mr Stoljar said there was "no submission" Mr Shorten engaged in criminal or unlawful conduct in his role at the AWU between 1998 and 2000.

TURC heard allegations of violence, bullying, bullets in the mail

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 14 seconds 7 m Trade union royal commission comes to an end

Unions including the AWU, the construction division of the Construction, Forestry, Mining and Energy Union (CFMEU) , the Health Services Union (HSU), Transport Workers Union (TWU), Electrical Trades Union (ETU), Communications Electrical and Plumbing Union (CEPU), Maritime Union of Australia (MUA), Shop Distributive and Allied Employees Association (SDA) and National Union of Workers (NUW) were examined in royal commission hearings around the country.

Several union slush funds were investigated.

There were allegations of violence, bullying, bullets in the mail and whistleblower turning on whistleblower.

Kathy Jackson from the HSU was grilled about her own use of members' contributions.

The CFMEU's construction division is expected to come under fire with the commission hearing evidence of cover-ups, corruption and stand-over tactics by some of its former officials.

The National Secretary of the CFMEU, Dave Noonan, told the ABC the two ex-officials at the centre of the most damning evidence "were dismissed from the CFMEU prior to the royal commission".

"We've made it clear that anyone who accepts bribes from employers will be sacked and expelled from the union and that's exactly what we've done," he said.

Mr Noonan said the royal commission had been "a very expensive exercise designed to drain resources away from the union".

Professor John Buchanan from the Sydney University Business School, who has in the past worked with unions told the ABC: "It was a poorly conceived commission, a highly partisan intervention designed to weaken the union movement."

He said while it had "uncovered some problems in some small pockets of the union movement, it hasn't found systemic problems across the entire movement".

"In responding to the problems identified, it's highly likely the union movement will be strengthened," Professor Buchanan said.