The former Chief Executive of the National Treasury Management Agency, Michael Somers, received a total pay package of €1m in 2008, including a bonus of €400,000.
In a decision to release the records, Information Commissioner Emily O’Reilly criticised the Department of Finance for the way in which the NTMA head's salary was decided, saying it should be more transparent.
Mr Somers retired in 2009 after 48 years in the public service, including 20 years managing the country's debt with the NTMA.
Details of his salary have always been kept secret, but have now been revealed to RTÉ News in a Freedom of Information request confirming that Mr Somers was the highest paid civil servant at that time.
Mr Somers received a salary of €565,000 and a bonus of €403,000.
He also received €30,000 as a Commissioner of the National Pensions Reserve Fund.
When the Department of Finance agreed to release these details one year ago, Mr Somers appealed that decision to the Information Commissioner, who said the information should be revealed because it concerned public money.
But Ms O'Reilly reserved some harsh criticism for the way the salary was decided.
The NTMA's advisory committee comes up with the figure and the Minister for Finance signs off on it.
She said the remuneration process was quite extraordinary and she criticised the fact that there is no paper trail supporting it no officials present at the meeting between the Minister and the Chairperson of the NTMA's remuneration committee.
Mr Somers' overall pay for 2007 cannot be revealed because the department has no record whatsoever of the figure.
The NTMA still does not reveal its top salary figures and has also been criticised this week by the Comptroller and Auditor General for hiring expensive advisors.
The confirmation that their pay has reached €1m will shine a further spotlight on the costs of the body in charge of NAMA.