There were a record number of potential downgrades last month and potential upgrades were at their lowest level since September 2004 as the credit crisis continued to take its toll, according to ratings agency Standard & Poor's.

Potential downgrades reached a record of 738 in May, which were 25 more than in April, according the ratings agency. The number is 118 higher than in the same period a year ago and 103 more than the average for last year.