According to security firm Sophos, the kits allow users to design sites that have the same look and feel as legitimate online banking sites that can then be used to defraud unsuspecting users by getting them to reveal the details of their financial accounts.
"By putting the necessary tools in the hands of amateurs, it's likely that the number of attacks will continue to rise," said Graham Cluley, senior technology consultant at Sophos.
Sophos warned that many of the kits also contain spamming software that enables potential fraudsters to send out thousands of phishing e-mails with direct links to their do-it-yourself fraud sites.
"The emergence of these 'build your own phish' kits means that anyone can now mimic bona fide banking Web sites and convince customers to disclose sensitive information such as passwords," Cluley said.
Many online banking Web sites now carry messages urging users not to open any e-mail that they suspect may be fraudulent and to telephone their bank for further information if they do receive suspicious e-mail.
Phishing has become such a problem that there are now several online antiphishing guides to educate users about the con artists' common tricks.
James Sherwood of ZDNet UK reported from London.