A new report on the activity of NAMA says the agency could have raised an extra €18bn for the taxpayer.
It is claimed the agency failed to realise a better return because it sold off many assets too quickly.
The research was found that 11 major sales to investment funds were then 'flipped' by the buyers with an average profit of 47%.
It says the taxpayer lost more than €300m on those transactions alone.
The study was conducted by Economist Jim Power and Lisney Estate Agency and commissioned by the Property Developer David Daly.