The Ministry of Justice has been hit by 500 age discrimination claims as the Public and Commercial Services Union (PCS) ramps up its pay campaign in the Civil Service.
The PCS claims a pay system introduced last year discriminates against younger members of the workforce as it can take more than 10 years for employees to reach the top of their pay scale.
The move comes just days before a one-day strike over low pay involving 260,000 civil and public servants across the UK on 10 November.
The union maintains the cases in the Ministry of Justice highlight the double disadvantage faced by public servants working for the Civil Service. Unlike other parts of the public sector, 'progression', or moving from the bottom to the top of a pay scale, is included in the government's pay cap, along with cost of living increases.
The PCS claims this means there is less money available to fund basic pay increases and movement up pay scales.
Mark Serwotka, PCS general secretary, said: "It is ludicrous that it could take over a decade for someone to get to the top of their pay scale and that long-serving staff should be penalised by getting no pay rise whatsoever."