Moody's has cut its rating of four Irish banks to junk status citing concerns over new funding which was due at the end of February.
The government says it will not make extra funds available before a general election on 25 February.
Opposition parties, who may form the next government, have expressed opposition to further bank aid.
Bank of Ireland, Allied Irish Banks, EBS Building Society and Irish Life and Permanent have all been downgraded.
Anglo Irish Bank and Irish Nationwide, which already have junk status, have been cut further.