Fitch Ratings is considering a downward revision in the long term credit ratings of Australia's major banks, a step that may cost one of them an 'AA' class rating. At present, Fitch has long-term credit ratings for Commonwealth Bank, National Australia Bank and Westpac of AA. Fitch rates ANZ at AA-.Fitch said that it "expects that any downgrades of the four major Australian banks' ratings are most likely to be limited to one notch with those entities currently rated at 'AA' most at risk."Should the downgrading proceed it will leave ANZ with a long-term credit rating of A+ from Fitch, and Commonwealth Bank, National Australia Bank and Westpac will each have an AA- rating.The announcement by Fitch of what it calls a "rating watch negative" on Australian bank ratings follows a review of its credit ratings of banks in Canada and Australia, and takes into account similarities in industry structure and economic fundamentals in both countries.Most banks in Canada have slightly lower credit ratings from Fitch than those in Australia, and the firm has come to the view that our domestic banks "continue to have a weaker funding profile than other similarly rated peers."Standard & Poor's cut the long term credit rating of the four major banks to AA- to AA. This followed a review of its own methodology, which, among other things, rated the economy of Canada more highly than that of Australia.