Former Australian Labor Party president Michael Williamson has pleaded guilty to funnelling almost $1 million from the Health Services Union (HSU) to businesses he had an interest in.

Williamson, who was arrested when detectives raided his Maroubra home in Sydney's east last year, now faces jail for the offences.

The police investigation probed allegations of corruption during his time at the HSU aired by the union's national secretary, Kathy Jackson.

He was accused of dozens of offences, including money laundering, dealing with the proceeds of crime and dishonestly dealing with hundreds of thousands of dollars of union funds.

Williamson appeared in Sydney's Downing Centre Local Court this morning with his solicitor Vivian Evans.

The prosecutor told Chief Magistrate Graham Henson that several offences had been folded into four formal charges that Williamson would plead guilty to.

Williamson admitted funnelling nearly $340,000 into a business called Canme Services, which was registered in his wife Julieanne's name.

Dozens of cheques were made out to Canme for services that were never provided to the union.

He also admitted to defrauding the union out of $600,000 through a consulting company called Access Focus.

It is believed Williamson received a massive windfall from the company due to inflated fees billed to the HSU.

The former unionist also pleaded guilty to fabricating invoices to cover his tracks in returns to the union in February last year.

Caught shredding evidence

The final guilty plea came in relation to recruiting of other union members to help destroy evidence and hinder a police investigation.

Last year, Williamson was caught trying to shred documents when he was confronted by the NSW Fraud Squad at the union offices in Sydney's CBD.

He has pleaded guilty to recruiting Carron Gilleland to help him destroy evidence in the case.

'Absolutely outrageous nepotism' SMH investigative reporter Kate McClymont broke the story that led to the charges. She has told the ABC it is a case of "absolutely outrageous nepotism". "Especially when you think that the members of the HSU are hospital cleaners, orderlies, among the lowest paid unionists in the country," she said. McClymont is not surprised Williamson pleaded guilty, saying there were "certain pressures put on him" to do so. "For instance, his son Christopher was one of those that was possibly facing criminal charges. So I think that there has been some argy bargy going on over the last couple of months that has led to his guilty plea today," she said.

Williamson stayed quiet through the proceedings today, with the prosecutor informing the court of the amended charge sheet.

He emerged from court speaking on a mobile phone and ignored the hive of media that had assembled.

Williamson resigned from the HSU late last year, less than two weeks after a leaked report into the union's internal workings alleged he engaged in nepotism by funnelling union funds to himself and his family.

The report, by Ian Temby QC and Dennis Robertson, detailed allegations of multi-million-dollar instances of nepotism, maladministration and cronyism.

It said Williamson had a salary of almost $400,000 and alleged five members of his family were among the union's best paid employees.

The magistrate committed Williamson to sentencing on October 28 in the District Court.

Police have previously said they expect to make more arrests in the case.

Closure for union members

The Australian Council of Trades Union (ACTU) says it hopes Williamson faces the full force of the law.

ACTU president Ged Kearney says he deserves whatever punishment he receives.

"Defrauding union members of their money is something that the union movement cannot abide and will not stand for," she said.

"These offences are very serious and we're very pleased that they will be dealt with properly by the criminal law."

The New South Wales secretary of the HSU, Gerard Hayes, says today's guilty pleas by Williamson will help bring closure for the union's members.

"There are 30,000 victims in this matter," he said.

"They needed closure and this certainly brings closure for them."