The earth moving digger is believed to have been stolen from a site on Sunday in Leicestershire before being used yesterday lunchtime to force entry to the rear of the bank.
The four-strong team of raiders in balaclavas smashed through the back of the bank in the digger after driving it along the high street.
They then drove off in a blue BMW car before stopping a silver Corsa and forcing a woman and her young child from their vehicle before driving away in it.
Police would like to hear from anyone who saw the digger being driven to the bank and anyone with any information is asked to contact Detective Sergeant Bob Jamieson at Nuneaton Local Investigations on 02476 483184.