Mandate is to picket the South African embassy tomorrow unless it grants trade union recognition and agrees to negotiate on a 25 per cent pay claim for staff.
Mandate represents five of the eight non-diplomatic staff at the embassy in Earlsfort Terrace, Dublin. According to the union's divisional organiser, Mr Albert Murphy, the employees have not had a pay rise since 1998.
Fifteen years ago the union, then known as IDATU, fought a two-year battle with Dunnes Stores to vindicate its members' right not to handle produce from the apartheid regime in South Africa.
When the former president of South Africa Mr Nelson Mandela was made a freeman of Dublin he thanked the IDATU members for their support.
Mr Murphy said yesterday that Dunnes Stores members would be showing their solidarity with members at the embassy if the strike went ahead.
According to Mr Murphy, the ambassador, Ms Melanie Verwoerd, had asked him at a meeting on Monday if the strike would be a token protest. He made it clear the strike would be continuous and, if necessary, prolonged.
In common with other embassies in Dublin, the South African embassy has refused to recognise trade unions. The 1961 Vienna Convention grants immunity to embassies and diplomats from the laws of the host state.
Ironically, in South Africa, union recognition is mandatory where employees demand it.
Mr Murphy described the decision of the South African embassy to use the Vienna Convention as "a spurious position to adopt. The embassy must choose between applying the very enlightened and pro-trade union position reflected in its country's own Bill of Rights and constitution or, alternatively, operating within the norms of the Irish industrial-relations structures. The South African Embassy cannot have it both ways."
Ms Verwoerd was not available for comment last night but when Mandate sought recognition in December, she said:
"While the South African government is committed to fair terms and conditions of employment for all employees, it is not in the interest of the South African government, or its employees, to make any further public statement about this matter."