It was a tragedy that most believe was avoidable.

Jack Brownlee and Charlie Howkins were killed in a trench collapse at Delacombe, near Ballarat in March.

"Jack was king of the jungle, that's the way he was remembered, the king of the jungle, the junkyard dog," his father Dave Brownlee said at a workers' memorial at Trades Hall in Melbourne on Friday.

"And he lived his life as best as he could.

"It's just a total tragedy that someone so young can be cut so short."

Lana Cormie's husband and Dave Brownlee's son were killed in the industrial accident. ( ABC News )

Mr Brownlee and Lana Cormie, Mr Howkins' widow, are backing a union campaign for new industrial manslaughter laws to hold bosses of companies responsible.

"Employers need motivation to do the right thing because clearly they don't do it off their own back,'' Ms Cormie said.

Jack Brownlee and Charlie Howkins died when a trench at this worksite collapsed. ( ABC News )

"If this will be the difference between them making OHS (occupational health and safety) a high priority and not, then it needs to be done."

So far this year, nine people have died at work, Trades Hall secretary Luke Hilakari said.

Under laws being pursued by Trades Hall, directors and managers would be held responsible and jailed for the death of workers on industrial worksites.

Unions across Victoria have launched a campaign to pressure the Andrews Government to follow the lead of Queensland and the ACT and the UK, to introduce industrial manslaughter laws.

'Stop the carnage'

Currently fines are handed out to companies where deaths occur on worksites, but unions want tougher punishments including jail terms.

The unions want to make the issue a prominent part of their election wish list ahead of the November state poll.

The shoes of those killed in workplace accidents were part of the union memorial. ( ABC News )

As part of the memorial, boots were placed on wooden stools to represent those killed this year.

CFMEU secretary John Setka said "too many workers are being killed".

"As a deterrent, more than anything, I think if you bring people to account for their actions I think we are going to stop the carnage," he said.

Laws introduced in Queensland last year include up to 20 years imprisonment for an individual and a maximum fine of $10 million for a corporate offender.

In 2014, Melbourne Water was fined $400,000 after Tim Bakerov drowned in a sludge channel at the organisation's Eastern Treatment Plant after falling through a walkway because there was a missing grate.

In his decision, Judge Chris O'Neill cited that Melbourne Water knew there had been a number of incidents over several years, noting missing or displaced grates on the walkways.

Judge O'Neill said "despite the evidence of reports of these prior occasions, no steps were taken to investigate the risk of slatted grates becoming dislodged and no consequent steps taken to secure them.

"In my view this was a clear and substantial failure, in particular in a workplace where there were considerable hazards and occupational health and safety matters were said to be important," he said.

'Important' election issue can't be ignored

With major infrastructure projects underway and more planned Trades Hall secretary Mr Hilakari said it was critical to make workplaces safer.

"There is work going on 24/7," he said.

"With so much work going on right now we need to make sure we have the best health and safety laws in the country and that means we need to introduce industrial manslaughter legislation.

"The State Government should be leading by example; saying that those who break the law by endangering working people will be held accountable.

"Worker safety will be an important election issue that politicians just can't ignore."

Wreaths for the nine workers killed on the job this year were laid at the memorial. ( ABC News )

Minister for Finance Robin Scott said Cabinet had not yet discussed the matter.

"But it is a very serious issue and we are certainly very committed to occupational health and safety and making sure workers come home,'' Mr Scott said.

Greens MP Nina Springle said the current laws were not working.

"Where corporate negligence results in serious injury or death, decision makers must be held to account for that negligence," she said.

"Our current laws are failing to do that, and in cases where serious negligence results in death, we're seeing big corporations fined as little as $150,000."

Opposition spokesman David Morris said the Coalition was happy with the current workplace rules.