A vast majority of online banking customers use their login credentials to access other websites, sharply increasing risk of attack to their bank account, Internet security firm Trusteer said on Tuesday.

Some 73 percent of Internet bank clients share online banking password with non-financial sites, and 47 percent re-use both, their online banking user name and password, British firm Trusteer said, citing a sample of more than 4 million users.

Our findings were very surprising, and reveal that consumers are not aware, or are choosing to ignore, the security implications of reusing their banking credentials on multiple websites, said Trusteer's Chief Technology Officer Amit Klein.

Michael Paisley, the head of information security at Santander in Britain, said banks protection shield has expanded beyond banks walls as online banking has increased.

From the bank's point of view it has become very important we help our customers to protect their identity online, he said.

Trusteer's Rapport browser security service -- which recognizes when users attempt to submit online bank credentials them to other websites -- is used by major North American and European banks.

(Editing by Sharon Lindores)