Fair Work Commission vice-president Michael Lawler has resigned on the eve of his deadline to respond to a report on his controversial use of paid sick leave.
Mr Lawler has been embroiled in controversy for taking paid sick leave from his $435,000-a-year job while helping his partner - disgraced ex-union leader Kathy Jackson - defend a lawsuit over large-scale theft from the Health Services Union.
His resignation on Thursday was a day before he was due to respond to the report.
The report, by barrister and former judge Peter Heerey, was the result of a four-month investigation.
Employment Minister Michaelia Cash told the Senate on Thursday afternoon that Mr Lawler had tendered his resignation to the Governor General Peter Cosgrove.
"Mr Lawler's resignation commences with immediate effect," she said.
The resignation also followed police reports that a 40-year-old man was found dead in Ms Jackson's home this week.
The death is not being treated as suspicious.
Ms Jackson last year lost a long-running Federal Court case and was ordered to pay about $1.4 million after Justice Richard Tracey found she stole money from the union she led.
She was found to have spent hundreds of thousands of dollars on unauthorised expenses including clothes, fine dining, grocery and liquor shopping, personal mortgage repayments, as well as flights and hotels while on multiple overseas vacations.
Police in Victoria are now investigating Ms Jackson for alleged criminal theft and fraud.
Ms Jackson and Mr Lawler shot to attention again last October after appearing in an extraordinary interview on ABC's Four Corners, in which Mr Lawler revealed he had been secretly recording his phone conversations with his boss.