An urgent investigation has been ordered into industrial relations practices at the National Gallery in Dublin, which has been beset by a series of disputes with its 130 staff.

Adjudicating on the latest dispute to hit the troubled gallery, Labour Court chairman Kevin Duffy said: "It is clear to the court that serious issues exist around the functioning of the HR [human resources] department, which should be addressed as a matter of urgency."

Duffy proposed the appointment of an assessor to "investigate the role, functions and practices of the HR department" who would report back to the court within three months.

In March the Sunday Tribune reported that a major row had broken out in the gallery after staff found a secret camera installed in the staff locker area.

The camera was disguised as a motion sensor on a wall but was discovered by a staff member who traced wiring back to a video recorder. Management said that wine had gone missing from official functions held at the gallery in Merrion Square.

The staff claimed that the camera was in breach of their rights and in breach of data-protection guidelines.

Management conceded that the camera was not placed properly and negotiations with staff are understood to be at a sensitive stage over the hidden device.

The gallery also got into trouble last year when an individual breached security and hung a nude painting of Taoiseach Brian Cowen on the gallery wall.

Last January, staff and management were again at the Labour Court, this time over the refusal of management to allow 50 attendants to expand their duties to include work in the gallery's security control room.

But management said allowing the attendants access to the control centre would compromise security at the gallery, which houses millions of euro worth of paintings.