The Community and Public Sector Union (CPSU) is blaming cuts to Victoria's public service for tens of thousands of motorists avoiding speeding fines.
It has been reported that motorists are escaping the fines because infringements officers cannot keep up with demand for reviews within the legal timelines.
The union's Karen Batt says the Government has cut 10 to 12 per cent of support staff out of paperwork processing roles.
She says similar issues are affecting a number of government departments.
"It's counter-productive and it's counter-intuitive to what the Government says is its initiative to cut the costs of the public service," she said.
"We believe that labour hire in the public service is undermining both the integrity of the public service and the ability to deliver services for Victoria."
But the Assistant Commissioner for Traffic, Bob Hill, has disputed the union's claims.
He says although staff are contracted in, it has been done in the past and it is not affecting fine enforcement.
"At this point in time, while we have those 40,000 infringements that are subject to the internal review, we have not withdrawn any," he said.
"We are still meeting our legislative requirements to ensure those reviews are completed within the three-month timeframe."