The three were on Swanston Street shortly before 3pm on a Friday afternoon when a strong gust of wind brought the wall down.

All died of head injuries after they were struck by the falling wall.

Mr Jones and Dr Fiawoo both died at the scene, while Ms Jones died later at Royal Melbourne Hospital.

Witness Jonathan Lian was metres from the wall when it fell, and on Thursday said further laws were needed to protect pedestrians.

Melbourne’s many construction zones reminded him of the tragedy, he said: "Sitting here looking out the window on my house I can see at least four apartments under construction."

The families of those who died began proceedings in the Melbourne Magistrate's Court against Grocon, but withdrew when the company indicated it would contest their claims.

Grocon was contacted on Thursday over the coroner's findings. It did not respond by deadline.

A subsidiary of Grocon was fined $250,000 in 2014 over the collapse, after pleading guilty to failing to provide a safe workplace.

In 2016, contractor Aussie Signs Pty Ltd was fined $250,000 in the County Court after pleading guilty to a charge of failing to ensure people were not exposed to risk.

Allan Robinson, the principal at Montmorency Secondary College where Bridget and Alexander went to school, said their loss was still "heavily felt" by staff and students who had known them.

"We were all shocked by this tragic event which is deeply imprinted on the history of our college," he said. "Their parents, Ian and Sue, are respected enormously ... and they continue to support the college and its students in all sorts of ways."

Federal Workplace Minister Craig Laundy said he hoped lessons had been learnt from the deaths.

“It was a dreadful accident,” he said. "It shouldn’t have happened."

The federal opposition's industrial relations spokesman Brendan O'Connor said the incident exemplified why workplace safety "has to be the paramount concern at all building sites".

At the time of the collapse, Grocon was engaged in a bitter dispute with the militant Construction, Forestry, Maritime, Mining and Energy Union, which has been fined millions for its behaviour on building sites.

Its state secretary John Setka said the coroner's report highlighted that not enough was done to crack down on companies that failed on safety.

"If you kill people, you get a slap on the wrist. If you are out there like us trying to save people, you get fined millions of dollars. What does that say about politics in this country?" Mr Setka said.

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Two years before the wall's collapse, Grocon engaged Aussie Signs to construct hoarding and signage for the wall. Aussie Signs sub-contracted the work to another company, which in turn sub-contracted the work again to another firm, Paramount Signs.

Judge Hinchey found that the onus to ensure the wall's structural stability rested with Grocon because it owned the site.

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She also noted in her ruling that new building laws introduced since the deaths would reduce the chances of a repeat accident.

Building laws changed in 2016 and now land owners and builders must ensure a building permit is in force and work is carried out according to law.

The 3.2m-high advertising hoarding commissioned by Grocon was up to 70cm taller than the brick wall it was attached to.

A subcontractor hired to attach cladding to the wall, Jonathon Westmoreland, was also fined $7500 in 2015 after being found guilty of performing works without a building permit.

Victorian Trades Hall Council secretary Luke Hilakari said the tragedy showed industrial manslaughter laws were needed, because "big companies will put profit before the safety of workers and the public".

With Erin Pearson, Simon Johanson and AAP