I contacted the Department of Foreign Affairs regarding the issuing of diplomatic passports.
I requested the name, position and passport date of issue for all current holders of such passports.
This request was refused on the grounds that the information was too voluminous. I was, however, advised that I could submit a Freedom of Information request on the matter.
I also requested the official definition of a diplomatic and an official passport.
In response I was provided with this link which outlines conditions for the issue of such passports which is, effectively:
For the purpose of travelling abroad in connection with official duties on behalf of the State.
Or, the minister may grant a diplomatic passport to:
A person, or one of a class of persons, to whom the Minister considers it appropriate to issue such a passport.
The key words in this last condition are, of course:
One of a class of persons.
This would probably explain why the likes of Mrs. Haughey, wife of the criminal politician, was granted the privilege.