And Attorney-General Simon Corbell told hundreds of building workers yesterday that his government still had work to do in reforming its procurement process so that safety comes before price.

About 600 construction workers marched on the Legislative Assembly yesterday morning to demand improved safety on Canberra's building sites.

At the centre of the CFMEU-led action was a tribute by Griffith woman Kay Catanzariti to her son, Ben, killed in an accident on a Kingston Foreshore construction job in July, aged just 21.

Ben Catanzariti was the fourth man to die on Canberra worksites since last December and the union has vowed to continue its campaign until meaningful reforms are enacted.

The workers gathered at Glebe Park and marched through the streets of Civic waving placards calling for an end to the ''bloodshed'' and led by Mrs Catanzariti, her other son Jack, her husband Barnaby and a lone bagpiper.

Describing her family as ''broken'' by her son's death, Mrs Catanzariti told the crowd that she was determined to fight for safety in the construction industry.

''There now lies a numbness within that cannot be expressed with words … no words can express the gut wrenching loss, despair and emptiness that now fills our lives,'' she said in her address.

''Ben can never return to us, but if my efforts today can prevent another senseless workplace accident from happening, then no other family will be broken like ours.''

Mr Corbell addressed the rally, along with ACT Greens MLA Amanda Bresnan and the Canberra Liberals' Vicki Dunne, with all three main parties throwing their support behind the inquiry into workplace safety in the territory.

''About two weeks ago we established an inquiry to get to the bottom of why it is that some companies … in the construction sector are prepared to trade off safety for their profit margin,'' Mr Corbell told the crowd.

''It's not acceptable, we want to get to the bottom of it and that independent inquiry is now up and under way.''

The minister also conceded that more reform was needed on the process of awarding government building contracts.

''We've already gone through a process where procurement is focused on those employers who are demonstrating good workplace safety.

''But that paper-based system now needs to be translated into better results on the ground.''

CFMEU ACT branch secretary Dean Hall said the ''race to the bottom'' in the construction business had to stop and called on the ACT government to place greater emphasis on safety and less emphasis on price when awarding civil contracts.