Further evidence that female workers were being paid less came after Government statistics showed that women were earning 54.2 per cent of their male colleagues' basic weekly earnings.
The Banking Insurance and Finance Union said women's salaries had shrunk since 1995 and it called on employers to root out discrimination.
Jo Seary, of BIFU, said: "Far from catching up, women in finance are falling further behind in pay. That's very often because women are still largely confined to the lowest paid grades.
"Contrary to popular belief low pay is a serious problem in the finance industry - almost one in eight staff earn less than pounds 4 an hour."
While women now outnumber men in the workplace for the first time in peacetime history, the Government New Earnings Survey said female managers experienced slower wage rises.
In 1993, women in senior positions earned 67.3 per cent of their male counterparts and that figure has now fallen to 60.4 per cent.Reuse content