ABC

A new report says commercial investment in the ACT is slowing.

Access Economics' Investment Monitor for September says the value of projects under construction in Canberra is down more than 20 per cent on the same period last year.

The downturn comes after a spike in office building in recent years.

In total there is more than $5 billion worth of investment construction underway or planned in the ACT.

The report points to major engineering works underway including the $350 million Canberra Airport upgrade, the Cotter Dam enlargement and the water pipeline from the Murrumbidgee River to Googong Dam.

It says construction of the new ASIO headquarters on Constitution Avenue and the duplication of the Gungahlin Drive extension are also bright lights on the horizon.

Nationally, the report says the massive Gorgon gas project in Western Australia has boosted what otherwise would have been a sluggish investment scene.

It says while business confidence is rebounding from the global economic crisis there is yet to be a broad lift in investment intentions.

During the September quarter there were only nine new projects listed on the Investment Monitor database nationally.