Sitting in Melbourne for the first time, the royal commission examined allegations, first revealed by Fairfax Media, that private information of hundreds Cbus members was leaked to the union.

Lisa Zanatta, a Cbus co-ordinator, said on Monday that CFMEU's NSW construction division secretary, Brian Parker, had called the super fund seeking data on workers as part of an inquiry to determine if the company Lis-Con was late in paying worker superannuation.

Mr Parker previously denied seeking or receiving any leaked member information when Fairfax Media revealed in May that the personal details of more than 300 workers of Lis-Con were leaked by Cbus last year.

Ms Zanatta, who was responsible for collecting the private information of industry super fund members, said she did not know how it ended up with CFMEU officials and that she was fulfilling a request for membership information from her superiors. She said Cbus wanted superannuation payments made monthly, but the company wanted to pay quarterly.

"It didn't come from me," she said when asked if she leaked private information to the union.

"Perhaps the union themselves had telephone numbers ... Can't you get phone numbers from the White Pages?"

Cbus and the ACTU seized on comments from Ms Zanatta that the membership details were sought to help track down superannuation entitlements that had not been paid, saying the commission should be expanded to investigate superannuation arrears.

Tuesday's hearings will examine claims of union intimidation and harassment at the former Pentridge Prison building site with key whistleblowers, whose concerns were raised to Fairfax Media last week, due to give evidence –including developer of the prison site, Peter Chiavaroli.

A KPMG report tendered during Monday's hearing found that Cbus released members details 68 times between January 2013 and May this year.

Counsel assisting the royal commission, Jeremy Stoljar, SC, said workers had faced threats and intimidation as a result of the leak.

At the start of the hearing, the union's counsel John Agius, SC, that media reports last week about evidence to be heard this week was a "matter of grave concern". He indicated that the leaks had come from within the royal commission and that it must be investigated.

He said the untested accusations leaked to the press had trashed the reputation of union officials.

But commissioner Dyson Heydon dismissed calls for an investigation, saying there was "no support whatsoever" to the union's claims that royal commission officers or witnesses were sources.

Outside court, the CFMEU branded the royal commission a political "distraction" from the Abbott government's unpopular budget.

"I think even blind Freddy knows this is all about politics," the national secretary of the CFMEU's construction division, Dave Noonan, said.

"The Abbott government set this up in order to deflect attention from their budget. They knew they were going to have a horror budget, they knew they would need a distraction.

Mr Noonan said the CFMEU was proud of its role in recouping millions of dollars of superannuation entitlements a year.

"Tens of millions of dollars are ripped off from workers every year by employers who don't pay or underpay superannuation entitlements in the construction industry," he said.

"Our union takes this very seriously ... We don't make an apology for it; in fact, we are very proud of it."

Mr Noonan said Cbus had a "very clear" policy around the provision of limited information for unions  seeking to recover money owed to workers.

"The fact is that the regulators in this space – the Australian Tax Office and Fair Work Building and Construction – are asleep at the wheel," he said. "If they were doing their job there would be a lot less money for the union to go around and recover."

WITH RICHARD WILLINGHAM