CFMEU ACT branch secretary Dean Hall said Canberra workers for two of Hastie's 44 subsidiary companies, Heyday Group and Border Stainless Steel, had already been affected by the collapse.

Mr Hall said about 60 electricians employed by Heyday on the new ASIO site on Constitution Avenue had been stood down this morning.

"They were called in today, they were told to pack up this morning and come to the yard where they were told last week's pay was their last," he said.

"So virtually they've been laid off.

"On top of this, you've got about 30 sub contractors on that site and while they were working this morning, we don't know for how much longer."

Mr Hall said a further 30 Heyday staff on the Centrelink project in Tuggeranong had also been stood down.

"This is the big point - Hastie is a parent company for all these other companies that are now being put in jeopardy as well," he said.

"This will have far more of an impact than St Hillier.

"Hastie owns companies that are heavily geared with labour and workers and Hastie and their sub contractors employ a lot of people."

Mr Hall said it was not unrealistic to expect that hundreds of ACT workers and their families would be affected.

"There'll be a knock-on effect as well with their sites because the other trades won't be able to complete their work because Hastie or their subsidiaries' work will prevent them from going forward," he said.

"For example, plasterers won't be able to complete a wall because ducting hasn't been finished and the knock-on effect is those contractors will then stall and those workers will be put at risk."