The incident took place at about midday.
A woman in her 70s was using a cash machine inside Lloyds Bank when she was approached from behind by a man who pushed into her and distracted her attention. The offender has then managed to withdraw a large amount of money from the victims account before fleeing the scene.
The offender then left the scene on foot along The Parade towards Dormer Place.
The victim was not injured during the incident.
The suspect is described as an Asian man, aged between 25 - 35 years old, of a slim to medium build, 5ft 6ins in height and clean shaven with short dark hair.
He was wearing a royal blue coat or anorak and dark jeans.
Anyone with information is asked to call Warwickshire Police on 101 quoting 148 of 25 February 2016.
Alternatively, information can be given anonymously to Crimestoppers via 0800 555 111 or the https://crimestoppers-uk.org/