Unions are demanding answers over the latest twist in the Michaelia Cash controversy, after it emerged a key figure in the government agency investigating the Australian Workers Union had been about to start a job in the employment minister's office.
Mark Lee works as a media adviser to the Fair Work Ombudsman but also does work for the Registered Organisations Commission - the Turnbull government body which ordered police raids on the AWU over 10-year-old donations to activist group GetUp!
Senator Cash's media adviser, David De Garis, resigned last week after admitting he tipped off the media the raids were about to happen.
The admission came after Senator Cash repeatedly told a Senate committee - under oath - that her office had not been involved in the leak. Labor has called for her to resign for misleading Parliament but she says Mr De Garis misled her.
Mr De Garis has not revealed where he got the information and now Australian Federal Police are investigating the source of the leak.
Now it has emerged that Mr Lee - who knew about the raids several hours before they occurred - was due to replace Mr De Garis in the media role in the coming weeks, as he moved to a different job in the office. Given the controversy, those plans have now been cancelled.
Fair Work Ombudsman Natalie James told a Senate estimates hearing last week Mr Lee had no contact with anyone outside the agency before the raids started, denying he was the source of the leak that sparked the whole embarrassing episode.
But ACTU secretary Sally McManus has written to Ms James demanding answers, saying there remains widespread suspicion about his involvement.
"Can the FWO explain how Mr Lee avoided the conflict of interest between his current employer and his prospective employer, Minister Cash, when he had access to highly politically-sensitive material last week?" Ms McManus wrote in the letter.
"If a widespread and understandable suspicion exists that Mr Lee was colluding with Senator Cash's office why would the FWO consider it appropriate to retain Mr Lee as a media adviser?"
Ms McManus also asks how unions can have faith in the ombudsman when Mr Lee had plans to "work for the very minister responsible for launching political attacks on trade unions".
"Can you explain why when you appeared before Senate estimates last week you did not see fit to reveal this highly relevant piece of information regarding Mr Lee's career plans?"
Mr Lee has not commented publicly on his involvement, but an FWO spokesperson said it was his decision not to take up the job.
"Mr Lee will continue to carry out his normal duties as media director at the Fair Work Ombudsman.
"It is common for departmental or agency staff to be engaged in Parliamentary offices."
Mr Lee is also friends with another of Senator Cash's media advisers, and they worked together in the office of former Victorian premier Denis Napthine.
Opposition Leader Bill Shorten was head of the AWU and also on GetUp's board when the union made $100,000 in donations to the activist group. The investigation centres on whether the donations were made following the union's proper procedures.