It is like the campaign period once again as Prime Minister Tony Abbott attacked the Labor Party in a threat he said will expose the dark corners of the party.

The Prime Minister is cooking a royal commission inquiry to Labor's relationship with corrupt officials.

On top of the watch list were the alleged slush funds by union leaders to fund the election campaigns for Julia Gillard in 1990 and payments to companies associated with top Labor officials in the wake of former Health Services Union boss Michael Williamson admission of defrauding the union of $1 million.

These activities were going to be the focus of the royal commission, more than investigating misbehaviours of Labor MP and Hsu leader Craig Thompson. Mr Thompson was allegedly paying for prostitutes with his union credit card, although, he had not pleaded guilty to the 145 charges of fraud and theft against him.

Former High Court judge Dyson Heydon was assigned to lead the commission. The inquiry was expected to happen in a year. Commissioners were mum when asked how much the inquiry will cost the taxpayer, but as records reveal, the same inquiry in 2003 amounted to $66 million.

"There've been very credible allegations, including allegations from senior officials in the union movement, of widespread corruption, standover tactics, even organised crime penetration. We're on the side of the honest unionist, we're on the side of the honest worker against the dodgy official," Mr Abbott told the Sky News Viewpoint program.

He strongly called out for the Opposition Leader to be vocal on which side he is supporting as former national secretary of the Australian Workers Union.

"Mr Shorten is a former union official himself and as things stand it looks like Bill Shorten wants to run, to coin a phrase, a protection racket for a protection racket," Mr Abbott said.

As for Mr Shorten, he expressed that the issue should be better handled by the police and not by high-ranking officials from the commission.

"In recent days and weeks, we've seen issues of corruption, of bribery, extortion, of outlawed motorcycle gangs in the construction sector. The best way to deal with these issues without a doubt is to support our police to do their job. This is a job for the police, not a job for the politicians."

For ACTU President Ged Kearney, he claimed that peak union body had "zero tolerance" for corruption but upheld that this is an issue that should be taken care of by the police.

"The real issue unions are fighting for is to ensure that wages keep up with the cost of living, and the government has spent the last few weeks attacking ordinary factory workers and their take-home pay," she said.

Attorney-General George Brandis, meanwhile, said that police and royal commission can both handle the issue separately.

"I think there's been growing public concern about corruption in the trade union movement which has accelerated in the recent past, and I think it would be frankly irresponsible for the government not to respond to that growing public demand in a very thorough way, marshalling all of the appropriate institutions to address the problem," Senator Brandis said.

Mr Abbott said that the police might take longer for the issue to be look into.

"The desert sands advance more swiftly than some of these investigations. And as we have seen with other serious problems, serious criminal law-enforcement problems, sometimes you need to shine a big spotlight, a great big spotlight, into the dark corners of our national life."