The 'Opening the Vaults' study, completed in conjunction with the Fair Finance Guide International, shows that banks reporting in Ireland made over €2.3 billion in profits on €3bn of turnover in 2015.
This 76% profitability rate is four times higher than the global average – only the Cayman Island had a higher rate with 167%.
The report of Europe's 20 biggest banks stated that:
"The 16 top European banks operating in Ireland examined in the research paid an average effective tax rate in Ireland of no more than 6% – half the statutory rate of 12.5% – with three banks (Barclays, RBS and Crédit Agricole) paying no more than 2%."
It named Luxembourg and Ireland as the "most favoured tax havens" in Europe, accounting for 29% of the profits banks posted in such areas in 2015.
The 20 biggest banks posted €4.9bn of profits in Luxembourg in 2015 – more than they did in the UK, Sweden and Germany combined.
Read more: Oxfam claims Ireland is a tax haven for banks | Newstalk