Thefts and assaults at Melbourne train stations hit a five-year high in the first year the state's protective services officers hit the beat.

According to Victoria police data, 716 assaults were reported at Victorian train stations in the past financial year, up from 596 in 2008/2009 and 688 in 2010/2011.

The first round of PSOs were deployed in February 2012 as part of the state government's pledge to deliver 940 PSOs to Melbourne and major regional train stations by November 2014.

The government says the rise in figures represents an increase in crime detection.

"It's an absolute reality that our train stations are safer because of the PSOs," Victoria Premier Denis Napthine said.

"And I go around on those stations at night and people tell me they feel safer; they are safer because of the presence of these hardworking PSOs."

But the state opposition says the government has failed to protect Victorian commuters.

"Train travellers would rightly feel concerned for their safety as Denis Napthine's law and order agenda falls apart," opposition police spokesperson Jacinta Allan said.

"No amount of spin ... can hide the facts that crime at train stations have risen under the Napthine government."

Ms Allan said cuts to Victoria police had put pressure on PSOs.

Victorian Greens leader Greg Barber says the increase represents a failure of the policy.

"They were supposed to be there to protect us, not write reports," Mr Barber said.

As of November 1, 508 PSOs were in service at 79 train stations.

A government estimates committee in June heard the cost of the PSOs was estimated to be about $300 million, including $78 million for infrastructure and about $5 million for advertising.