The calle comes 24 hours ahead of a crucial meeting between the financial institutions and Finance Minister Brian Lenihan about the future of the lenders.
A consortium of private equity investors and a rival group of fund management companies are proposing investing in some banks.
ICTU says these investors would be focussed on short term and their investment would lead to massive job losses.
Congress says the Government should borrow money to nationalise and recapitalise the banks.
It says the National Pension Reserve Fund should not be tapped for the investment - instead it suggests Ireland borrows the money.
General Secretary David Begg says mismanagement of the banks would result in colossal economic damage.
He added: 'It beggared belief that Government could even countenance investment from venture capital and private equity funds - precisely the same sources which have brought about the current international crisis.
'You only have to look at eircom and our deficient communications' infrastructure to realise the damage these people could do to the banking system.'
However, private equity investors have told Government they would be ring-fence money for new lending to help the economy.
While unions favour full scale nationalisation, Mr Lenihan says putting public money into the banks is his least favoured option.
