Management at St Vincent's University Hospital in Dublin is preparing to seek a High Court injunction to prevent shop stewards and officials of the Irish Nurses' Organisation (INO) from meeting with staff in clinical and patient care areas.
Separately last night, hospital management also instructed nursing staff who are on paid leave to serve on the INO industrial action co-ordinating committee to return to work from today.
It warns that such staff who fail to go back to normal duties will be taken off the payroll and "may be subject to other formal procedures".
The threatened actions, if they proceed, could have implications for the talks being chaired by the National Implementation Body, aimed at finding a solution to the current dispute.
The INO has accused management at St Vincent's of seeking to harass and intimidate members.
It has also described the actions of management as "provocative and hostile".
An emergency meeting of nursing staff is to be held today at St Vincent's.
Under rules governing disputes agreed between unions and health service management in 2004, staff can be given paid leave to serve on committees dealing with contingency plans for industrial action.
The INO has said that there are around 12 whole-time equivalent staff available to serve on its co-ordinating committee at St Vincent's, which has over 1,200 nursing personnel.
Hospital management has contended that the size of the committee at St Vincent's is much larger than in other hospitals.
A spokesman said that the committee could not be used as a mechanism to remove key people from posts in the hospital.
It has also maintained that there have been complaints from staff regarding members of the co-ordinating committee having access to clinical areas.
The INO has claimed that it is established practice for unions to meet members in clinical areas. It has also argued that management has failed to provide details of any complaints.
It said that by last night, more than 600 nurses had signed a petition objecting to management's move to ban the trade union from meeting staff in clinical areas.
In a letter to the INO on Monday, hospital management said that it wanted the union to cease carrying out trade union business in clinical and patient care areas.
Management had sought an undertaking in this regard from the INO and, in a letter sent yesterday, said that the failure of the union to provide this left in with no option but to proceed with its plans to seek a High Court injunction.
Management sources said that the timing of any move to secure an injunction would be determined by whether the INO continued to access clinical areas in St Vincent's.
The INO said in a letter last night that the "decision to seek an injunction is ill advised, unnecessary and unreasonable. Having spoken to colleagues in other hospitals, there is no such restriction in place", it said.