An impromptu memorial has been set up in Victorian parliament to mark the 50th anniversary of the West Gate Bridge disaster, the state’s worst industrial accident.

Flowers and cards were left in Queen’s Hall to remember the 35 workers who died and their 18 injured colleagues.

At 11.50am, a 112 metre span of the bridge gave way during construction and fell into the Yarra River.

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The Australian and Victorian flags on top of the bridge are lowered to half mast from 7am to 7pm every October 15.

The accident had a major impact on the construction industry, with many safety initiatives introduced as a result of the disaster.

Independent MP Andy Meddick said the memorial was set up in Queen’s Hall for the union movement.

“It’s extremely important that we remember the worst industrial disaster that this state … has seen,” Mr Meddick said.

“It was seminal in how this country and this state then dealt with the rights of workers.

“So many of the strides that the union movement has made in the rights of workers in all workplaces stem from that moment.

“It certainly changed the construction industry.”

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Prominent union official John Setka said his father was one of the survivors who rode the span as it crashed to the ground.

“We’ve come a long way when it comes to enforcing safety on worksites, but the enormity of this tragedy will never be forgotten,” Mr Setka said.

State Workplace Safety Minister Ingrit Stitt said the anniversary is a tragic reminder of how dangerous workplaces can be.

“(It’s) why it’s so critical to constantly renew our commitment to safety in every Victorian workplace,” Ms Stitt said.

A commemoration at the West Gate Memorial Park in suburban Spotswood, near the site of the accident, is on hold because of Melbourne’s lockdown rules.

The park was opened in 2004 to honour the victims of the accident and to increase awareness of workplace safety.

-AAP