While some union leaders did not support Victorian construction union secretary John Setka's view that his union has secured "fantastic pay rises and good conditions for members because we fight outside the law", there was broader support for his call to repeal the "draconian" secondary boycott laws.

Although the criminal case against Mr Setka collapsed this week, the Construction, Forestry, Maritime, Mining and Energy Union (CFMMEU) has paid $10 million in penalties and fines over boycotts and blockades it organised against concrete company Boral during the union's high-profile dispute with Grocon. Boral refused to meet union demands that it cease supplying Grocon.

Mr Setka told Fairfax Media that the anti-competition laws governing secondary boycotts were "draconian".

"It means if a union or members are being oppressed you can't step in to help them out," he said.

"I think it is a very bad law. It was brought in by ultra conservative governments and should be repealed."

On Friday several powerful unions signalled their support for changes to the law with the ACTU saying the current regime did not meet International Labour Organisation (ILO) conventions that Australia has signed.

“Australian law is out of step with global standards in our bans and restriction on industrial action, including so-called “secondary” action," the ACTU said.

“The International Labour Organisation has called on the government to review these laws but they have not."

Australian Manufacturing Union national president Andrew Dettmer said secondary boycott laws even prevented unions negotiating across multiple sites.

"It really militates against us bargaining across industy which is how other advanced capitalist nations such as Germany bargain," he said.

Mr Dettmer declined to comment on Mr Setka's statement about breaking the law to achieve better pay and conditions for members.

AMWU state secretary Steve Murphy agrees there "needs to be a rethink about secondary boycott laws".

"Employers are allowed to organise and build power across an industry or a supply chain, but workers are contrained from responding by secondary boycott laws," he said.

"What we are seeing is the emergence of a new generation of union leaders across the country, who are more explicit about having laws reflect the natural right of workers to organise and to build power. In a way we are going back to basics: and the right to strike is part of that."

Transport Workers Union national secretary Tony Sheldon said secondary boycott laws needed to be changed to deal with companies that unilaterally outsource work.

"It's clear when employers can economically damage their own employees by outsourcing their jobs without notice, then employees should have a right to take action and that means secondary boycott laws need to change to allow that happen," he said.

Mr Sheldon said wages were declining and workers needed to have a right to stand up against unfair outcomes.

He said the Fair Work Act which came into effect in 2009 before the emergency of the on-demand economy which is "gaming the system".

Other unions voiced support for Mr Setka's view that laws sometimes needed to be broken to achieve industrial goals.

Electrical Trades Union national secretary Allen Hicks said industrial and consumer laws needed to change because . He said his members, and those of the CFMEU, who worked in dangerous industries "have to do everything we possibly can to best represent our membership in that space".

"People are not going to give 24 hours notice before entering a work site because that's what the law says if someone's safety at risk," he said. "Employers are breaking the law every day of the week by underpaying workers and not paying superannuation."

NSW Nurses Association general secretary Brett Holmes said his union took strike action in 2010 to introduce nurse to patient rations in defiance of a NSW Industrial Commission order.

"What delivered out of that was 1400 more nurses saving lives in our public health system," he said.

NSW Teachers Federation president Maurie Mulheron said teachers have defied orders against strike action under NSW industrial laws on a number of occasions.

"People felt the issue warranted strike action, but the laws are so punitive and restrictive we need to change them and give professions like the teachers access to industrial relations commission to have salaries aribrated. Even though there has been significant change in the work of teachers and increased hours and workload, there is no opportunity to legally run a work value case in the [Industrial Relations Commission]."

Labor's Workplace Relations spokesman Brendan O'Connor said Labor wants fairer and safer workplaces and would engage with parties to that end. "We also expect employers, workers and unions to comply with the laws of the land as no one is above the law," he said.

Mr Setka said his union would now do all it could to hold Coalition politicans, lawyers and companies involved in the alleged blackmail case to account.

Victorian state prosecutors dropped blackmail charges against Mr Setka and his deputy Shaun Reardon over the union's boycott of concrete company Boral.

Pending legal advice, Mr Setka said he would like to sue over the impact the legal case had on him and his family.

"I'd love to sue them if I could," he said. "My main aim is to go after them and to make sure they never do this to anyone again."

Mr Reardon echoed Mr Setka’s determination to pursue any politicians involved in the collapsed criminal case against the two men.

“The personal damage caused to members of my family from these charges borders on being criminal in itself,” Mr Reardon said.

“The CFMEU will leave no stone unturned in its endeavours to expose the political corruption that has seen a government so blatantly manipulate so many so called Independent agencies for its own political gain."

The CFMEU Victoria's lawyer Peter Gordon said there were "a number of potential causes of action" he wanted to explore.

Mr Setka said his union did  not set out to break the law.

"I believe in the law.... but over the history of mankind, people have always defied unjust laws," he said.

"If I have to go out and break a law so my member can go home safe to their families at night then that was what I have to do."

Mr Setka said the Rail Tram and Bus Union in NSW complied with the law when it followed a Fair Work Commission order to call off a 24-hour strike in March.

"They followed the law and they got screwed," Mr Setka said.

"If they did what we do they probably would have won.

Mr Setka said the Rudd Labor government was the worst in history and had used "anti-union law firm Freehills that were trying to set us up" to help draft the Fair Work Act 2009.

He said the union movement helped Labor get into power and it "screwed workers" in return.

"I know they are there to govern for all Australians, but why pander to big business so much? You don't see the Liberals pandering to the trade union movement," he said.

Workplace Minister Craig Laundy said Mr Setka wanted greater ability to shut down workplaces and for union officials to have free rein to enter any workplaces at any time.

“Mr Setka has made it clear the union movement isn’t happy with the Fair Work regime they designed with the Rudd/Gillard Government, so they want to ditch it in return for strikes and warfare not seen since the days of the Whitlam Government," Mr Laundy said.

One senior Labor Party figure privately conceded on Friday day that the party’s association with the CFMEU and its "macho" and "bully-boy aggression" was not a positive with voters.

In comments which lend some weight to the government's position, the figure said it was beyond doubt there were elements of the CFMEU in Victoria that were "corrupt".

"This is damaging to the Labor Party but other unionists say it is very damaging to the standing of their unions too," said the frontbencher.

The figure said it was clear the union in Victoria was part of local Mr Shorten's support base.

But another Labor source said the campaigning capacity of the CFMEU was formidable adding that "things would have to get a lot worse" before we told building and construction workers that they had no role in the ALP".