Victoria's pollution watchdog has failed to properly monitor air quality across the state with many highly-populated centres going unchecked, a scathing review has found.

A report by the Victorian Auditor General has revealed the Environment Protection Authority was unable to show that its data collection truly reflected the air quality experienced in most Victorian communities.

The audit analysed EPA data monitoring between 2010 and 2016.

Traffic on The West Gate Bridge. Credit:Pat Scala

It identified 40 urban centres, using 2016 Australian Bureau of Statistics data, that were not covered by the EPA’s air monitoring network.