The agency cut its ratings on the long-term debt of BNP and Credit Agicole by one notch to Aa3, concluding reviews that began in June and were continued in September. Societe Generale's long-term debt was cut by one notch to A1.
The downgrades were driven by the increasing difficulties the banks were having in raising funding and the worsening economic outlook, Moody's said.
The news comes a day after the European Banking Authority (EBA), warned the region's banks must find €114.7bn of extra capital in order to withstand the euro zone debt crisis and restore investor confidence.
Moody's said its ratings did take into account the fact that all three French banks were likely to benefit from state support if the crisis deepened.
"Liquidity and funding conditions have deteriorated significantly," said Moody's, adding that the banks have historically relied on wholesale funding markets.
"The probability that the will face further funding pressures has risen in line with the worsening European debt crisis."
By Jamie Dunkley taken from http://www.telegraph.co.uk/finance/newsbysector/banksandfinance/8945640/French-banks-downgraded-by-Moodys.html