The Government could be faced with a bill for millions of euros if significant pay increases sought by the Civil and Public Services Union (CPSU) are successful.
The union made its decision following an Equality Tribunal decision that seven female clerical officers in the Garda Síochána had been discriminated against because they received less pay than male gardaí who were doing "like work".
The CPSU, says the case provides the basis for further equal pay claims by 10,000 of its members in the Civil Service.
At the union's annual conference in Galway today, General Secretary Blair Horan told delegates the claim was part of the union's overall strategy to end the gender pay gap in the civil service.
This afternoon Mr Horan told RTE radio that he thought it was an "open and shut" case.
"The problem with government is allocating male workers traditional male grades like guards but also prison officers onto work of a clerical nature they [the Government] are exposing themselves to equal pay claims that will cost them millions over the years."
The union is expecting to have about 10,000 claims submitted over the next few months.
"There is no doubt about it the Department of Finance will fight it very hard but equally we would feel confident of ultimately being successful," Mr Horan added.