The eight men and five women were held during searches of 14 addresses in Ealing, Hayes and Hammersmith, in west London, and Bradford, West Yorkshire.
The swoop is part of a City of London Police investigation into a criminal gang suspected of opening bank accounts in false names, using false documents and then inflicting significant losses on those accounts.
The estimated loss to UK clearing banks and finance companies as a result of their alleged activities is believed to be in the region of £3 million.
A member of staff from a bank in Ealing was among those arrested today.
Officers also seized various items of property during the searches, including two high-value cars and banking documents.
Detective Sergeant Martin Peters said: "The City of London Police have a strong track record in the investigation of banking fraud.
"This investigation has focused on the addresses of a group of organised individuals, who have been fraudulently attacking the UK clearing banks by opening bank accounts in false names using false documents.
"We suspect that this gang has stolen nearly £3 million.
"During this investigation, we have been working closely with all the financial institutions. These liaisons have been invaluable in developing our inquiries.
"The City of London Police will continue to take a robust stance in targeting and dealing with gangs that target the financial industry."