The former head of the National Treasury Management Agency, Michael Somers, received a total pay package of €1m in 2008. This included a bonus of €400,000.
In a decision to release the figures, the Information Commissioner criticised the Department of Finance for the way in which the NTMA chief'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 as the chief executive of the NTMA - the agency which manages the country's debt.
Details of his salary have always been kept secret but have now been revealed to RTE News in a Freedom of Information request, confirming that Mr Somers was the highest paid civil servant at that time.
His 2008 pay comprised 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 Emily O'Reilly, who said the information should be revealed because it concerned public money.
But she 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 was no paper trail supporting it, and 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.
