From the Australian @ABCNews:

Big four banks warned they may be downgraded by Fitch because of reliance on offshore funding

The Coalition and its sympathisers regularly take credit for the reforms instituted by Hawke and Keating, but what's really kept the coal-fired Australian juggernaut moving are mineral exports to booming markets, and a ready pool of cheap foreign credit. Banks could take money from depressed markets with low interest rates, then charge Australians local rates. Obviously, this disparity fuelled a gravy train like… a train powered by gravy. Mmm, gravy!

As for ratings agencies: well, I've voiced my opinion of them before, especially with regards to Ireland.