Worksafe Victoria is investigating claims that asbestos materials were left unsecured near a childcare centre in Melbourne's west.

Workers say they noticed what was believed to be large amounts of broken asbestos sheeting in piles of construction rubble at Altona last week.

Workers at the Millers Road site and a nearby childcare centre were alerted immediately.

Union officials advised the management of the childcare centre to keep children away until further notice.

CFMMEU Victoria occupational health and safety unit manager Gerry Ayers says it was a horrific situation.

“In this day and age it is atrocious that cowboy operators can show such a blatant disregard for the safety of their workers and the general public,” he told the ABC.

“We have advised the management of the childcare centre next door that children should not play outside until further notice, and that they register their potential exposure through the national asbestos, dust fumes and chemicals register.”

Worksafe Victoria says it “has visited the site to ensure the removal of any asbestos containing materials is appropriately managed”.

Reports say the material has now been covered over, after sitting exposed for several weeks.