The Australian Financial Markets Association has re-elected ANZ, Commonwealth Bank, National Australia Bank and Westpac as its prime banks.The number of AFMA prime banks was cut from six to five last December, when JP Morgan Chase was removed from the list. This followed a decision by Standard & Poor's to downgrade JP Morgan Chase Bank NA from AA- to A+. Under AFMA's rules, a bank must have a minimum S&P rating of AA- to be eligible as a prime bank.Then, in February, the number of prime banks was cut again, to four, when BNP Paribas requested that it be removed from the list.