The Canadian Council of Independent Laboratories says some projects involving highways and other infrastructure currently underway in Ontario don't require independent testing or inspection of their quality and safety.
The group calls it "a serious and potentially dangerous mistake" because there's no assurance that the materials and construction meet standards and is urging the government to change the rules.
An independent expert panel has said it can't determine whether 500 girders used in the construction of the $1.4-billion Windsor parkway are safe and durable.
The government says it won't replace them, but will monitor and fix the girders as necessary.
NDP Leader Andrea Horwath says the council's warning is alarming and independent inspections should be mandatory for all infrastructure projects.