STATE training agency FAS has hired an external company to investigate whether former director Greg Craig was wrongfully suspended.
The agency has now taken on the professional services of Mazars following a complaint from the FAS's former director of corporate affairs.
Mr Craig was suspended after an internal audit investigation, which is still ongoing, uncovered concerns about financial controls within his corporate affairs division.
A separate investigation is continuing at FAS into allegations of misconduct against 15 present and former employees, including Mr Craig.
As head of the department, Mr Craig controlled an annual budget of more than €10m.
The former director revealed that he first knew about his suspension when he heard it on the news.
Assistant director general Christy Cooney announced the fact to the Public Accounts Committee (PAC) amid criticism over the expense bills of senior executives at the State's employment agency.
A total of €642,000 was claimed on expenses for travel to the US between the years 2004 and 2008.
A letter confirming Mr Craig's suspension did not arrive until a few days later, he said.
He was centrally involved in many of the decisions which led to millions of euro being overspent and wasted by the agency over the past decade.
Now the cost of taxpayer-funded probes could run into tens of thousands of euro.
Union representatives objected to the manner in which Mr Craig was suspended and he was reinstated a short time later. In a letter forwarded to FAS, Siptu said the suspension was in breach of established disciplinary procedures at the state training agency. The union also sought a meeting with FAS management to discuss Mr Craig's situation.
Mr Craig was subsequently moved to a new role as a health and safety officer after the corporate affairs division was broken up.
However, after he lodged an objection, Mr Craig was reinstated and his suspension was recategorised as "administrative leave".
External management consultant Ignatius Lynam is investigating the actions of 15 present and former employees, including Mr Craig.