THE MAJOR construction union in the ACT has revealed apprentices, and not their bosses, are generally the people on worksites identifying potentially deadly asbestos.

It comes as the ACT government weighs up when it will introduce legislation to the Legislative Assembly to make an asbestos identification training course mandatory for all construction workers.

There are countless tonnes of potentially deadly asbestos in Canberra.

In the past year asbestos has been uncovered at Lyneham sports precinct, along Constitution Avenue on the site of the new ASIO headquarters, in units at the Kingston Foreshore and in the new Molonglo suburbs.

In 2010, close to 300,000 tonnes of asbestos-contaminated soil was found at the North Weston Ponds area - a dangerous dump the ACT government is now preparing to sue the Commonwealth over.

The secretary of the ACT branch of the Construction, Forestry, Mining and Energy Union, Dean Hall, said his organisation was prepared to subsidise union members to do the half-day detection and awareness course.

Mr Hall said asbestos training on a smaller scale had already proved remarkably successful.

Asbestos training already provided to apprentices in the ACT had led to most of the discoveries of asbestos on worksites.

''It's a fantastic initiative, well overdue,'' Mr Hall said.

''According to the statistics, asbestos-related diseases in Australia won't peak until 2020.''

If the training does become compulsory, the territory branch of the union is planning to use a kitty, which could be worth as much as $100,000, to help workers get the accreditation.

Industry observers expect the legislation to be debated next year.

Before then, perhaps in the next few months, it is expected the ACT Work Safety Commissioner Mark McCabe will issue a guidance notice to employers.

The note will tell them that they should teach their workers how to identify the dangerous substance.

The notice is not legally binding but is still expected to influence employers and act as a warning of the expected legislative changes.

The ACT branch of the Master Builders Association is generally in favour of the proposal, but is still looking at the detail.

The association's deputy executive director Jerry Howard said, while a number of members were in favour of the proposal, others had put forward the argument training for their particular trades would be needless.

The executive director of the Construction Industry Training Council, Vince Ball, said thousands of ACT construction workers would already be accredited and would not have to do more training.

However he estimated 4000 or more would still need to be trained.