Just as rating agencies thought the fuss over their failure to spot impending corporate disasters at Parmalat, Enron and WorldCom had gone away, the controversy has returned.

At the end of last month, Parmalat filed a legal complaint against Standard & Poor's, alleging that the agency had made an inaccurate rating in the run-up to Europe's biggest bankruptcy at the end of 2003. On the same day, Eliot Spitzer, the New York state attorney-general, issued a subpoena to Moody's as part of his probe into insurance company ratings.