Moody's Investors Service has downgraded the long-term ratings of six Canadian banks. 

The banks affected include: Bank of Montreal, Bank of Nova Scotia, CIBC, TD Bank, Caisse centrale Desjardins, and National Bank of Canada.

The long-term senior debt ratings of the six banks were all downgraded by one notch.

Moody's says the downgrade reflects ongoing concerns about the banks' exposure to the ``increasingly indebted Canadian consumer,'' while elevated housing prices have left the banks ``more vulnerable to unpredictable downside risks facing the Canadian economy than in the past.''