... is there an agency that represents the interests of the people who have to live day by day beside anti-social behaviour, which is ignored by the landlord?
Landlord refuses to engage with residents, ignores telephone calls from Gardai, has lied about the status of the tenancy.
You can bring a third party case against the landlord through the PRTB(www.prtb.ie).
A landlord is legally responsible for a tenant's anti-social behaviour. There are several third party cases reported on the PRTB website that are worth looking at. The main thing seems to be to prove that the landlord is making no attempt to control the tenant's behaviour so document all your contact with him. As the Gardai are involved it is obviously behavior that would be considered as anti-social and not something trivial that could be dismissed in a case.
Does this case need to be taken by an individual or can a committee or other third party do it?
The individual concerned has shown themselves to be violent and people are understandably afraid to get involved.
You should ring the PRTB and have some initial discussion with them about how to go about bringing a third party case. My understanding is that the case has to taken by an indidvidual or group of indviduals directly affected by the anti-social behavior.
Unfortunately, Mel, the case can not be taken by any Residents Association or other body. It needs to be an individual. I say this based off my own investigations in making an application for the disclosure of a landlord's details, it makes it quite clear on those forms that individuals must complain. Also, should this end up in Mediation/Arbitration, then meetings that the tenants are entitled to attend may come up.
With this in mind, and assuming there is more than one individual being negatively affected, I would think getting everyone with an interest in this (i.e. your other neighbours) on board is a good idea, and get them to make their own complaints. It costs €25 but sounds in your case as if it will be worth it. Also, I believe that a finding in your favour can result in compensation to you.
Thanks for your information.
We'll just have to keep phoning the gardai - there is no residents association, and people don't want to get involved in anything that will bring them to the attention of these nasty individuals, landlord and tenant. Some people appear seem to be above the law, and those affected just have to put up with it.
Edited to add - put up with it or be labelled a snob.