A man has been found dead in the home of former Health Services Union boss Kathy Jackson, police have confirmed.

It is believed the 40-year-old man died from a medical episode and the death is not being treated as suspicious.

The man did not live at the home. Police told The New Daily the man was thought to be a friend of Ms Jackson and her partner, Fair Work Commission President Michael Lawler.

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Police were called to the Wombarra home, north of Wollongong, just before 11:30am on Wednesday.

The Daily Telegraph reported, based on an unnamed source, that the man appeared to have died of natural causes, possibly in his sleep.

Ms Jackson was the national secretary of the Health Services Union of Australia (HSU) between January 2008 and February 2015. She was successfully sued by the HSU in the Federal Court for misappropriating union funds and ordered to pay $1.4 million in compensation in 2014.

An appeal by Ms Jackson to overturn this order was dismissed in December 2015.

The court heard she used that money to fund a lavish lifestyle. She was also ordered to pay back almost $70,000 of overpaid salary.

Mr Lawler and Ms Jackson were the subject of a bizarre Four Corners episode. Photo: ABC

Ms Jackson was once described as “a lion of the union movement” by Christopher Pyne after she blew the whistle on Labor MP and former HSU official Craig Thompson.

Mr Thompson was eventually found guilty of 13 charges of theft. He spent HSU money on prostitutes and fine dining.

An appeal by Mr Thompson was later dismissed.

In 2011, Ms Jackson took concerns to NSW Police that eventuated in former HSU and Labor Party national president Michael Williamson being sentenced to seven-and-a-half years in jail.

Ms Jackson and Mr Lawler were then the subjects of one of the most bizarre Four Corners episodes ever seen on the ABC in October 2015.

During the program, Mr Lawler admitted he had secretly recorded conversations he had with Fair Work President Ian Ross since 2012. He also admitted he had benefited from HSU paid accommodation and airfares while with Ms Jackson.

Ms Jackson still denies wrongdoing.

-with AAP