The nation’s biggest building union has referred what it claims may have been leaks about witnesses and evidence from the Trade Union Royal Commission to the Australian Federal Police for investigation.

On Tuesday, the Construction, Forestry, Mining and Energy Union (CFMEU) said it had written to the AFP asking them to investigate how media outlets and friendly witnesses appeared to obtain information about the nature of evidence to be presented by the Royal Commission into Trade Union Governance and Corruption before it was heard.

In a statement, CFMEU National Construction Secretary Dave Noonan said the union was alarmed at what he says are growing indications of possible leakage from within the Commission, adding that the union’s concerns had been dismissed by the Commission.

“We have raised these concerns in the Royal Commission. Commissioner Dyson Heydon dismissed them out of hand and suggested we go to the police, so we are taking his advice,” Noonan said.

“We are gravely concerned about the conduct of this Royal Commission.”

The latest moves follow a series of allegations levelled at the union during Commission hearings earlier this month, including that the union pressured builders in the Melbourne apartment construction market to boycott Boral after the company continued supplying to Grocon whilst Grocon was locked in a bitter dispute with the union.

The union raised alarm when a Fairfax Media report published on July 3 alleged the CFMEU’s Victorian boss John Setka had bullied a Melbourne builder into employing his brother in law as a shop steward and that unions used backroom dealings to bully workers into joining and pressure managers into coercing non-members to join.

Noonan says the CFMEU is concerned about media outlets reporting on private hearings and the nature of evidence before it was heard, which he says suggests media have access to information not available to subjects of the Commission’s hearings.

He says the union has also provided the AFP with a sworn statement from an employee of construction industry superannuation fund Cbus raising concerns that witness and former union official Brian Fitzpatrick had been briefed on the direction of the Commission’s hearings and individuals to be subpoenaed before subpoenas were issued.

But the Office of the Royal Commission has rejected the claims.

In a brief statement provided to Sourceable, the Commission said its Chief Executive Officer Jane Fitzgerald rejected any idea information about the direction and conduct of its hearings had been leaked, and stood by a July 7 statement in which she emphatically denied the Commission had briefed any journalists about operational matters, including the then forthcoming meetings in Melbourne.

Still, Noonan said the issues raised were serious.

“I urge the Australian Federal Police to take this matter seriously and investigate the management of information within the Trade Union Royal Commission as a matter of urgency,” he said.