The NTMA's withdrawn stockbroking firm Davy's authority to act as primary dealer in Irish Government bonds, with immediate effect.
In a statement, the board of the National Treasury Management Agency says the decision was based on its assessment of the very serious findings relating to the firm that were made by the Central Bank last week.
It follows engagement with investors in Government debt over recent days.
Over the weekend, three senior executives resigned from Davy after the company was fined €4.1 million by the Central Bank for breaches of market rules.
Minister for Finance Paschal Donohoe says he notes and supports the decision taken today.