When a senior official raised concerns about a union slush fund and dodgy dealings he was told by a young Bill Shorten to think about his future, a royal commission has heard.

Robert Kernohan was in 1996 also bullied at the Australian Workers’ Union, a union corruption inquiry has heard.

He was sent three bullets in the mail and bashed by at least three men when it became known he was planning to go to the police with concerns about union bank accounts and the sale of a property.

“Keep your f****** mouth shut. Stop talking to the press, you grub,” the men yelled during the July 1996 beating, Mr Kernohan said in his statement to the royal commission into union corruption.

Mr Kernohan’s worries began earlier in 1996 when he was served with a subpoena to attend the Federal Court in Sydney as one of 20 defendants in an action launched by the AWU.

Former union official Bruce Wilson has a run-in with a photographer outside a royal commission hearing in Sydney last month. Photo: AAP

He had accepted $6500 in a meeting that “took no more than 30 seconds” from notorious union figure Bruce Wilson, to help with AWU election costs.

Mr Kernohan said he rang Ian Cambridge, then an AWU official investigating irregularities in the union’s accounts, “and told him the genesis of the $6500.”

“I told him that a lot more has been going on than I have been made aware of and I’m the (AWU) president (in Victoria),” he said.

“I also told him I would be going to the police.”

Mr Kernohan said his friend and campaign manager Bill Shorten had at the time told him he was “lined up to take a safe Labor seat of Melton in the Victorian parliament.”

When he raised concerns about the Sydney court proceedings, Mr Shorten said “Bob, think of your future,” according to Mr Kernohan.

“If you pursue this, a lot of good people will get hurt and you will be on your own.”

Mr Kernohan said that was the end of his political ambitions.

“Any chance I had of entering parliament … I knew that had evaporated the minute I walked away from Bill Shorten,” he told the commission.

Outside the commission hearing on Wednesday, an angry Mr Kernohan continued to slam the AWU.

A Royal Commission has heard explosive allegations about former Prime Minister Julia Gillard and members of her cabinet.

“A fraud, a cover-up, a scandalous cover-up that resulted in Nicola Roxon, Bill Shorten, Stephen Conroy ending up in the Gillard cabinet,” he told reporters.

“People have got to ask themselves would that cabinet have been constructed the way it was had this been properly investigated all those years ago and, more importantly would Julia Gillard have become prime minister?”

Mr Kernohan said Mr Shorten, who has said police and not a royal commission were the best way to investigate union fraud, would never be prime minister.

“Once this matter is properly investigated and recommendations are handed down by this royal commission Bill Shorten will be exposed for what he is, just another key player in the cover-up over all these years.”

Mr Kernohan said current AWU secretary Bill Ludwig was the “most powerful ALP figure in this country”.

“It was Bill Ludwig who installed Julia Gillard into the prime ministership of this country. Bill Ludwig knew full well about the scandal … and for that he should be condemned,” he said.

Mr Kernohan said there were “two frauds perpetrated.”

“The first was on the Australian Workers’ Union and its members.

“The second was on the Australian people.”