Young father Tim Macpherson identified as rigger who died on a barge at Darling Harbour

Mr Macpherson, 32, was standing on the barge just before 4.25pm when he was crushed by a large piece of steel.

He suffered critical injuries to his head and torso and died at the scene.

Brian Parker, the NSW secretary of the Construction Forestry Mining and Energy Union, said Mr Macpherson had been working as a rigger on the site for six months - a role that involves securing objects to a crane before they are lifted.

He was watching as a heavy metal beam was lifted by a crane, when it knocked into another beam, which toppled and hit him.

"One header beam was attached to the crane, so it's got chains which lift it, and that has hit another header beam that wasn't secured. So it was sitting in the air on two pylons. That has then fallen over and crushed the worker," Mr Parker told Fairfax Media.

"Obviously the workers are very traumatised. I've spoken to a number of workers and I know they're all receiving counselling as we speak.

"My understanding is there's not going to be any work on this particular project tomorrow."

Mr Macpherson had a young family and had recently moved into their new home near Maitland.

Mr Parker said the union was in close contact with his family and would work closely with investigators to determine how the incident happened.

“We've seen a spike in the amount of deaths and serious injuries in the industry,” he said.

“Every nine minutes [across Australia] there's been a severe injury to a worker or a death. Already the death tally across the country is running at one per week.”

Mr Macpherson was part of a crew building a ferry hub at Barangaroo which is expected to open in the first half of this year. That particular construction site is not operated by LendLease, who oversaw the construction of the rest of the Barangaroo project.

Police, paramedics and workers remained at the scene, which is next to a public path and several restaurants, for several hours after the man died.

Ten News reported the incident unfolded in front of hundreds of people along the busy strip.

Water police and detectives inspected the barge, where a tarpaulin was placed next to the large piece of steel and concrete thought to have hit the man.

Minister for Transport and Infrastructure Andrew Constance said he was “deeply saddened” to learn about the worker's death.

“In this horrific time for the man's family, friends and colleagues I would like to pass on my deepest sympathies and thoughts,” he said.

“I trust our NSW government agencies will co-operate fully with all investigations into this very sad incident.’’