The fourth-year apprentice electrician is believed to have suffered serious head injuries on Tuesday after he received an electric shock and fell five metres from a ladder.

The man was working for a company contracted by the ACT government to carry out maintenance on the Dundas Street site.

It's believed he was working on a roller door when he was injured.

The Canberra Times understands the young worker has undergone two bouts of surgery at Canberra Hospital. ACT Policing and WorkSafe investigators have launched inquiries into the incident.

The accident occurred on the same day as up to 600 construction workers marched on the Legislative Assembly to protest against the territory's recent work safety record, which has seen four fatal accidents on Canberra worksites in 10 months.

Submissions closed yesterday to an inquiry into workplace safety in the territory.

Angry officials from the apprentice's union said they had long been worried about declining safety standards.

Electrical Trades Union official Mick Koppie said the territory's safety inspection regime was worked beyond its capacity.

''We don't want to make this into a political issue but WorkSafe ACT is overstretched and understaffed,'' Mr Koppie said.

''We've been severely restricted by various acts from going on to building sites and in what we can do.

''But union officials are generally industry experts from the industry.''

Mr Koppie said that all of the union's Canberra members were thinking of the apprentice's family.

''We certainly wish the family all the best and hope it works out well for them,'' the union official said.

Chief Minister Katy Gallagher said the accident showed that workplace safety laws needed to be fixed or more rigorously enforced.

''What this is saying to me is that people aren't taking these laws seriously enough or something needs to be fixed in the way our regulatory system works,'' Ms Gallagher said.

''I know the union wants to have the power to go in and close jobs down. But frankly I don't know if that is the answer. I'm not sure if that would necessarily improve workplace safety.

''But there definitely has to be something done, because this is not acceptable.''

ACT Work Safety Commissioner Mark McCabe said the incident highlighted the need for workers and employers to be vigilant.

''I am saddened to learn of the incident that occurred [on Tuesday] and it proves that dangers lurk in every workplace,'' Mr McCabe said.

''An incident of this nature is tragic and my thoughts are with the young man's family and friends at this time.''