The ex-Secretary General of the Department of Finance said personal attacks on civil servants over the Siteserv deal are "regrettable".
In a statement, John Moran's described comments made by former Irish Bank Resolution Corporation chairman Alan Dukes about him as "a step back to pre-crisis mindsets among bank management".
It comes after Mr Dukes told reporters his relationship with the Department of Finance deteriorated after a failed request by John Moran to join the board of IBRC, something Mr Moran has strongly denied.
Mr Dukes said he felt the appointment would not have been appropriate.
"I said to him: 'no, I think that would be a very bad idea, you'd be deeply conflicted.' He pointed out to me, quite correctly, that the Treasury in the UK had appointed a senior Treasury official on the board of Northern Rock.
"But he wasn't the person who was making banking policy for the Treasury. Had the Department of Finance wanted to appoint a civil servant from the department on to the board, of course that would have been perfectly in order, and it's been done before.
"But that wasn't what was proposed."
Yesterday, Dukes criticised Finance Minister Michael Noonan, after the Minister said the inquiry into the sale of SiteServ would investigate any criminal behaviour.
Dukes said it was outrageous to even suggest criminality, and that it was the first time he had ever faced such claims.