Garda Síochána Ombudsman Commission

As of the start of May, there is a Garda Ombudsman who deals with complaints about the Garda.
http://www.gardaombudsman.ie/

I assume, but am not sure, that they will deal with complaints about GNIB and the immigration officers at borders.

Let's try Ireland Ombudsman who deals with complaints against Irish Government Agencies as well.

http://ombudsman.gov.ie/en/