Safeil Maqbool, from Bury and Qasar Akhtar, from Bolton, worked for HBOS in Bury and were jailed for four and a half years and three years nine months respectively when they appeared before Bolton Crown Court. They pleaded guilty to charges of conspiracy to defraud.
A third gang member, Vincent Bagshaw of Haslingden, who also pleaded guilty to a similar charge, will be sentenced later .
The court heard that the men were able to copy account details of over 50 customers before they were apprehended.
HBOS officials gave evidence that more than £4m was stolen. Some of the money has been recovered.
The prosecution said the fraud was only spotted when one of the gang on the outside tried to draw a large sum that aroused the suspicion of bank staff. Bank investigators were then called in to discover how so much money could have been been taken undetec-ted and police were alerted.
A HBOS spokeswoman says: “We are very pleased with the verdict in this case. We would like to emphasise that it was our own monitoring teams that brought these events to light. We would also like to make it clear that no customers lost any money.”