A banking expert says if the Australian banks get a credit rating downgrade, it will impact on their New Zealand operations as well.

Credit Rating Agency Moody's is warning Australian banks are lending out money at a faster rate than they're taking in deposits, forcing them to increasingly rely on international funding markets.

That could have an impact on their credit ratings .

Massey University's David Tripe says the big four Aussie banks operating here are in the same boat.

"Over the last four or five years we have been taking in more deposits than writing loans, but there is still in effect a significant shortfall of deposits relative to loan volumes."