If you've ever parked at a train station, it's likely your number plate has been written down and scanned by police.

Protective Services Officers, who patrol many of Melbourne's train stations from 6pm to the last service, have also been tasked with scanning station car parks for expired registrations, unpaid fines and arrest warrants.

Protective Service Officers have been tasked with scanning station car parks for expired registrations, unpaid fines and arrest warrants. Credit:Rob Carew

Number-plate details are recorded and checked against Victoria Police's database in a move that has been slammed by Victoria's leading civil liberty group.

Anyone with an outstanding warrant may return to their car to find a sheriff waiting, and their car's wheels clamped.