The woman responsible for collecting the private information of union super fund members does not know how it ended up with union officials, a royal commission has heard.
Lisa Zanatta, a co-ordinator at union superannuation fund CBUS, said she was given more information than she asked for when asked to assess a Queensland company that owed money.
That information, including phone numbers and home addresses, ended up with the Construction Forestry Mining and Energy Union's (CFMEU) NSW branch.
Zanatta told the royal commission into trade union governance and corruption that she did not print out or email the information of CBUS members to CFMEU.
Counsel assisting the commission Jeremy Stoljar SC asked Zanatta if she knew how the CFMEU got hold of members' private data, including phone numbers and home addresses.
"It didn't come from me," she told the commission in Melbourne on Monday.
John Agius SC, for the CFMEU, also asked commissioner Dyson Heydon to investigate possible leaks from the commission, after evidence collected in private hearings was reported in the media last week.
Agius said the information could only have come from someone working within the royal commission who had access to private documents.
"It must be a matter of grave concern," he said.
Commissioner Heydon reserved his decision on whether to investigate the leaks.