Network Rail is facing an equal pay claim after bonuses for senior male staff topped £1 million.
More than 30 female managers have launched the claim, which is being backed by the union Transport Salaried Staffs Association (TSSA).
Female managers at the transport organisation are paid between £3,000 and £4,000 a year less than male colleagues doing the same job.
If the claim is successful, a further 3,000 women at the organisation would be in line for pay rises to bring their wages in line with those of their male counterparts.
The final bill could amount to more than £10 million a year if the TSSA is successful at the Leeds Employment Tribunal this autumn.
A spokesperson for Network Rail said: “Network Rail is committed to equal opportunities and fairness and equity in its pay.
“We are working hard, in partnership with trade unions, to address any legacy imbalances within our pay structure. Those discussions continue.”
Lorraine Ward, union assistant general secretary at the TSSA, added: “It is simply outrageous that a taxpayer-funded organisation should reward those at the top with such huge amounts while, at the same time, discriminating against thousands of its own staff who happen to be women.
“As a soon-to-be fully public sector organisation, [Network Rail] should reward everyone the same regardless of gender.”