Staff at EBS Building Society are to hold a second one day strike on Thursday, January 26th.
The action is in protest at the withholding of a 13th month payment in December, the equivalent of which was paid to management.
In an escalation of the dispute, the Unite trade union announced that pickets would also be placed at offices of AIB, the parent company of EBS.
Unite members at EBS decided on the industrial action at a general meeting this evening.
Unite regional officer Colm Quinlan said: "This is a dispute which should never have come about and our members are in no mood to back down. The withholding of wages only applies to staff at or below assistant manager grades with average earnings in the region of €30,000 per annum."
"The decision by EBS management, AIB or the Department of Finance was wrong. To have announced it two weeks before Christmas, having previously confirmed the payment would be made was cruel. It has generated a level of anger that is rarely seen in any workforce, let alone the banking sector."
Mr Quinlan told The Irish Times that the location of the pickets would be specified over the next week.
He said that union was allowing two weeks to create a window of opportunity for negotiations.
"Notwithstanding the fact that we had a one-day strike already, there has been no engagement anywhere. We have not seen the placement agreement upon which this decision was made. We are saying loudly and clearly, this will not be resolved without talks. If there are talks that lead to a solution there will not be a strike but we are serving notice now that there will be a strike if that is not the case."
He said in the forthcoming one-day strike, members would aim to minimise the effects on the public. However he warned that Unite would consider going to the Irish Congress of Trade Unions to seek an all-out picket at the company.