The Police Association Victoria said the Ringwood police station had been without six morning-shift van patrols and three afternoon-shift van patrols during the past two weeks.

Union secretary Senior Sergeant Greg Davies said the lack of shift van patrols followed a long-standing absence of regular foot, bicycle and vehicle patrols, which he said were rarely possible because of inadequate police numbers in the area.

"The only way that a minimal police presence has been maintained in the past few weeks has been to call on members to work overtime or do double shifts."

He said Croydon police had also been so under-resourced that patrol vans had not hit the road for at least two shifts in the past fortnight, and this was "not an infrequent occurrence".

A recent independent study by the National Institute of Economic and Industry Research found the Maroondah/Knox area needed an additional 71 police officers to provide sufficient proactive and reactive policing.

"To continue operating in Maroondah and Knox with the current number of officers must result in a further decline in the ability of those officers to deliver the most effective policing service to the community," Senior Sergeant Davies said.

The shortage claims follow reports from the union late last year that Croydon, Knox and Boronia police stations were unable to field patrols on consecutive days. "The situation is critical," Senior Sergeant Davies said.

"Maroondah and Knox are rapidly growing regions of Melbourne. Police numbers should be boosted urgently to keep pace with population growth."

Government spokesman Chris Owner said the Government had provided a $1.9 billion budget this year for police resources and rolled out a further 120 officers recently. "Where police resources are allocated is best left to the chief commissioner and Victoria Police, and not in the hands of politicians."