Updated - Health Minister Godfrey Farrugia has written to MUMN President Paul Pace telling him his actions in issuing directives which could affect patients were unacceptable.
The Health Ministry also said Mr Pace refused to attend a consultation meeting after wanting to dictate who sat at the table.
The minister's letter followed a strongly-worded statement by the union which criticised the minister for lack of consultation on a Strategic Business Unit for the management of Mater Dei Hospital.
The MUMN said it had directed nurses at Boffa Hospital not to get involved in the migration from Boffa Hospital to the new oncology hospital and to boycott any administrative instructions from clinical consultants.
It said it had issued the directives because of a lack of consultation by the health minister on a new Strategic Business Unit for the management of Mater Dei Hospital, and a decision to give some administrative responsibilities to medical consultants.
The union said the minister was repeatedly undermining the government's commitment to 'listen' because meetings were always about impositions, rather than consultations.
It said the minister had set up with the Strategic Business Unit (SBU) for Mater Dei, which would also include the new oncology hospital, but never sought the opinion of the union.
The union reiterated its view that the management of the oncology hospital should not be taken over by that of Mater Dei but should remain autonomous, as is currently the case with Boffa Hospital, which the new hospital will replace.
The MUMN also said it could also not remotely understand how the minister had decided to give the medical consultants administrative roles in the day-to-day running of their departments, especially when certain clinical consultants had a conflict of interest due to their private practice.
The union directed its members not to attend meetings or contribute to the migration of the new oncology hospital; Not to be part of the migration process when the patients are transferred to the new oncology hospital and to boycott any administrative instructions from the clinical consultants
The union said it was resigning from the management/union joint committee set up by the health minister since all decisions had been taken without having been discussed.
MINISTRY'S REPLY
In its reaction, the ministry said Mr Pace yesterday refused to attend a consultation meeting at the ministry to discuss the Strategic Business Units.
It said Mr Pace wanted to dictate who of the government's officials sat at the table.
Referring to the directives issued by the union, the ministry said that over the past months it had done all it could to maintain good relations with all trade unions. The minister remained ready for talks with all trade unions, including the MUMN.
In his letter to Mr Pace, Dr Farrugia insisted that the priority of everyone in the health sector should be the patient.
He said the union's directives affected the treatment of patients directly or indirectly.
"Even in matters of industrial relations, the union must act with good faith and in a proportional manner," Dr Farrugia said.
Health sector workers had a duty to do what they were ordered to do by their senior officers.
"Your actions in the context of vulnerable people are unacceptable and deplorable," the minister said.