Since a critical European ruling, tribunals have been inundated with 40,000 cases, 30,000 of which were launched in the fortnight before Christmas. The overwhelming majority of applications came from women, a majority of the five million part-timers in Britain.
In recent years, industrial tribunals have been processing about 60,000 cases a year and it is feared that the system will not be able to cope with the added workload.
Unions have warned that there are thousands more cases in the pipeline.
In September, the European Court of Justice ruled that it was unlawful to exclude part-timers from company pension schemes and that they could claim benefits as far back as 1976.
The Government expressed fears at the time that industrial tribunals would not be able to deal with the new workload and warned that the judgment would deter firms from taking on part-time workers.
All the big unions have delivered claims, including Unison, the public services' union, the Transport & General and Bifu, the banking union with a large female membership.
Bifu alone has lodged 2,500 applications and Ed Sweeney, its deputy general secretary, said employers were trying to use part-time staff as cheap labour and must now pay the price. "We've put a lot of effort into identifying part-timers affected by this discrimination and we want members who think they're covered to contact us."
More than 1,300 claims cover current and former staff at the TSB, which did not admit part-timers who worked less than 18 hours a week to its pension scheme until 1991. Mr Sweeney, however, said that all the high street banks were involved, as were many building societies.
"The employers could short-circuit this whole exercise by agreeing to backdate all pensionable service. They can afford to do that in the finance industry." Otherwise, the Government should put more resources into the tribunal system to help with "an avalanche" of claims.Reuse content