An equal-pay campaign that could cost the Department of Finance up to €12 million has been initiated by middle-ranking civil servants.
Up to 2,000 members of the Public Service Executive Union claim they were unfairly excluded from a €34 million equal-pay settlement between another union and the Department earlier this year.
The Civil and Public Service Union, which represents staff in lower-ranking clerical grades, announced that deal at its annual conference in May.
It followed a 12-year campaign on behalf of about 5,000 lower-paid civil servants.
The claim arose from the fact that until the late 1990s paper-keepers, most of whom were men, were paid about £50 a week more than clerical assistants, most of whom were women, for doing similar work.
The two grades were amalgamated into the clerical officer grade in October 1997.
The CPSU described the settlement as the biggest equal-pay claim conceded in Europe.
As part of the complex deal, all CPSU members who were clerical officers in October 1997, at the time grades were restructured, and had not been promoted since, qualified for payments of about €6,000 each.
The PSEU, which represents civil servants in the higher grades of executive and higher executive officer, claims the settlement discriminated against some of its members.
Mr Tom McKevitt, the union's deputy general secretary, said it believed that staff who were clerical officers in October 1997, but were subsequently promoted, were also entitled to compensation.
"They [the CPSU] were looking after their members, but the effect of the settlement was to exclude a whole lot of our members. That's what we will be arguing," he said.
The PSEU is currently inviting members who were promoted to executive officer between September 1997 and last May to fill in discrimination complaint forms.
When this process is completed, the union intends to take cases on behalf of members to an equality officer.
If it succeeds at that stage, it will seek a settlement from the Department of Finance similar to that agreed with the CPSU.
Mr McKevitt said up to 2,000 PSEU members would be eligible to make claims.
If 2,000 PSEU members were to reach a settlement equivalent to that agreed with the CPSU, the cost to the Department of Finance would be in the region of €12 million.