Mr Parker, who is nicknamed "Sparkles" for his reputation for mixing with the rich and famous, was reinstated as secretary of the NSW branch of the Construction, Forestry, Mining and Energy Union.

A spokeswoman for the union said Mr Parker  declined to comment further.

An interim report by counsel assisting the Royal Commission into Trade Union Governance and Corruption last year accused Mr Parker of "gross misconduct", saying he was "not a fit and proper person to hold office as the secretary of the NSW branch".

A media statement issued by the CFMEU last month announced that Mr Parker was standing aside from his position as secretary "in order to focus on matters arising in the royal commission".

"Mr Parker maintains that there has been no wrongdoing on his behalf," the statement said.

Mr Parker faces allegations of deliberately lying in sworn evidence to the commission when he denied threatening to "f---ing bash" a long-serving union delegate.

The royal commission is considering a possible recommendation that Mr Parker be charged with perjury after giving evidence that was directly contradicted in voice recordings played during hearings.

Mr Parker has also denied allegations of "concocting a plan" to obtain confidential documents revealing the personal details of Cbus superannuation fund members that were hand-delivered to his office

Late last year, he was forced to find his own legal representation after the CFMEU's legal team abruptly cut him loose, saying it could no longer represent him because of an undisclosed conflict of interest.

Mr Parker is expected to face questions about his relationship with Sydney underworld figure George Alex whose labour-hire companies have been linked with alleged payments to the union.

Witnesses gave evidence that the CFMEU allegedly received a weekly kickback of $2500 from companies linked to Mr Alex.

At his recent appearance before the commission, Mr Alex said there had been a failed attempt within the union last year to "roll" Mr Parker from his position.

Employment Minister Eric Abetz said Mr  Parker's history of dealings with George Alex and the damning royal commission findings that had already been made against him demonstrated that he was not a fit and proper person for the role. 
"His return to the role represents a serious failure of leadership by the national bosses of the union, Dave Noonan and Michael O'Connor," Mr Abetz said. 
"CFMEU members are being sadly let down by the union's current leadership, which has done nothing to address the serious problems of corruption and thuggery within their union. 
"This makes a complete mockery of the CFMEU's statement issued on Friday that they would deal with misbehaviour." 
Mr Abetz said Labor and the Greens needed to repudiate the union and return the "bucket loads of tainted money they have received from it".