Former AWU official Bruce Wilson has attacked a photographer outside the royal commission into union corruption in Sydney, where a fellow former union official has been giving evidence.

Day one of the commission, presided over by former High Court judge Dyson Heydon in Sydney, is probing the slush fund scandal that dogged former prime minister Julia Gillard.

The Abbott Government has given Mr Heydon the task of investigating union slush funds and one in particular set up more than 20 years ago by self-confessed union bagman Ralph Blewitt and fellow AWU official at the time Mr Wilson, who was also Ms Gillard's boyfriend.

At Monday's hearing, Mr Blewitt described handing over $7,000 in cash during a visit to Ms Gillard's Melbourne home in 1994.

"I arrived at the house, walked through the house to the back - the whole place was open," he said.

"My recollection is Julia Gillard was in one of the rooms adjacent to the front door. She said words to the effect [of] 'Oh, Bruce is through the back. Just go through'.

"I went through. I met Bruce Wilson in the kitchen/verandah area. There were three other people in attendance that day. They were doing renovations on either the verandah or the kitchen.

"Mr Wilson called out to somebody, who came in. He asked me to pay him $7,000, which I did. I counted off $7,000, gave it to that gentleman.

"He stuck it in the front pocket of his bib and brace overalls and went back outside."

Ms Gillard has previously denied that any union funds were used to pay for renovations on her home.

Outside the hearing, Mr Wilson was photographed engaging in an altercation with a photographer for The Australian, Sam Mooy.

The Australian newspaper reports Mr Wilson was eating lunch when he noticed two photographers taking photos.

Mooy and AAP photographer Dan Himbrechts say the attack was unprovoked and that Mr Wilson grabbed one of them by the collar and struck camera equipment.

Mr Blewitt and Mr Wilson are both accused of being behind a fraud in which hundreds of thousands of dollars from developers were paid into the slush fund and then siphoned off.

AWU money used to buy Melbourne house: Blewitt

Mr Blewitt also told the royal commission that he used $90,000 of AWU members' money to buy a Melbourne home.

He says he and his then-boss Mr Wilson established the AWU Workplace Reform Association primarily to raise funds for union elections.

Mr Wilson wanted to keep the association confidential and at arms length from himself, Mr Blewitt said.

"I did as instructed by Mr Wilson," he said.

"The whole thing was kept completely secret from anybody else."

Ralph Blewitt says AWU funds were used to put a deposit on a Melbourne home. ( AAP: Dan Himbrechts )

Mr Blewitt also told the hearing that funds linked to the slush fund were used to pay a 10 per cent deposit for a $230,000 property bought in Victoria in 1993.

He said despite the property being purchased in his name he did not attend the auction, saying Mr Wilson and Ms Gillard attended the auction.

The previous year, Mr Blewitt and Mr Wilson flew to Melbourne to gain legal advice from partners - including Ms Gillard - at the offices of law firm Slater and Gordon after their initial attempt to incorporate the association had failed.

Ms Gillard was involved in drafting the documents required to establish the association, Mr Blewitt said.

When asked by counsel assisting why a pair of Perth-based union officials would need to travel to Victoria or purchase a property there, Mr Blewitt said Mr Wilson was being relocated to help resolve internal problems within the union in that state.

He said there had been a period of political upheaval in the Victorian branch of the AWU and that Mr Wilson was also being groomed for a possible tilt at federal politics.

The AWU is the first of five unions to be examined over alleged bribery, kickbacks and slush funds within its ranks.

Mr Stoljar said everyone likely to be affected by Mr Blewitt's evidence has been told in advance but so far no-one else has sought leave to give evidence.

Gillard denies knowledge of slush fund's workings

Mr Wilson denies any fraudulent conduct and says he did not benefit financially from the slush fund in any way. Nor, he says, did Ms Gillard.

Speaking to 7.30 last year, Mr Wilson said Mr Blewitt had told him he had withdrawn some of the money from the fund and buried it in his own backyard.

In addition, in 2012, when the controversy dominated proceedings in Federal Parliament, Mr Wilson spoke out to dismiss claims that money from the slush fund was spent on renovations at Ms Gillard's Melbourne home.

"It just didn't happen. I mean, this gets recycled and recycled and recycled. Why it continues to get a guernsey is beyond me," he said at the time.

"Well, it's not beyond me, I understand there's a group of people intent on doing as much damage to the prime minister as they possibly can at the moment."

Sorry, this video has expired Watch Julia Gillard's press conference in November 2012 (AAP: Alan Porritt)

Ms Gillard also denied the claims, providing a detailed character assessment of Mr Blewitt.

"Mr Blewitt, according to people who know him, has been described as a complete imbecile, an idiot, a stooge, a sexist pig, a liar, and his sister has said he's a crook and rotten to the core," she said.

"His word against mine. Make your mind up."

However, claims about the former prime minister's involvement do not end with home renovations.

In 1995, Ms Gillard was a partner at Slater and Gordon, the Melbourne law firm which acted for the AWU.

She has said she provided advice on establishing the legal entity used by the two AWU officials for the slush fund.

But Ms Gillard has strenuously denied wrongdoing or knowledge of its workings prior to serious allegations being raised about it in 1995.

"Once I became aware that I had been deceived about a series of matters, I ended my relationship with Mr Wilson," she told reporters in November 2012.

On that occasion, Ms Gillard said she was unable to canvass further details about her involvement in setting up the slush fund because files held by her old law firm were covered by legal professional privilege.

Constitutional law expert Professor George Williams says the commission can demand a right to look at those documents to make up its own mind as to whether they are covered by legal privilege.

"That doesn't extend to a document where a court has previously declared the document is covered by legal professional privilege," he said.

"But that doesn't seem to be the case here, and that really gives the commission a very strong power to determine what sort of documents it will use in its proceedings."