According to a government-commissioned study, women at some of Britain's top banks and finance companies take home bonuses five times smaller than their male colleagues.
The average annual bonus for women was nearly 2,900 pounds (3,300 euros, 4,800 dollars) compared to about 14,500 pounds for men, the report carried out by the Equality and Human Rights Commission (EHRC) said.
The findings come after finance ministers from the Group of 20 largest and fastest-emerging economies called at the weekend for "global standards" on pay but stopped short of backing calls for bonuses to be capped.
The survey of 44 companies employing almost a quarter of the workforce in the sector also found that most women starting new jobs in finance companies received lower salaries than men.
The difference in pay for men and women of comparable seniority in firms surveyed was 39 percent, rising to 47 percent for total earnings when bonuses, overtime and performance-related payments were taken into account.
The study also showed that fewer than half the companies were making an effort to address the pay gap, with just one in four undertaking a pay audit to ensure women were not paid less than men.
Trevor Phillips, chairman of the EHRC, said: "The financial sector has the potential to play a central role in Britain's recovery but it has to address this shocking disparity of rewards.
"By bringing down arbitrary barriers, and changing practices that, intentionally or not, inhibit women's success, financial firms have the chance to boost morale, bring on new talent and maximize the potential of their existing employees."
Harriet Harman, Britain's minister for women and equality, said: "We cannot tackle discrimination if it is hidden which is why I asked the commission to produce this report.
"It's unlikely that men-only boards and management would ever deliver the change in working culture, such as family-friendly flexible working and childcare, that will allow women to flourish in the workplace."
She said the government was introducing legislation to force companies to reveal pay discrepancies between men and women.
Employers' representatives said the report showed progress needed to be made.
John Cridland, deputy director general of the Confederation of British Industry, said: "No sector is immune from tackling the gender pay gap and this report highlights that in parts of the financial services sector there is some further distance to go.
"But, as in many other areas of business, women applying for the top jobs need more flexibility with hours and childcare responsibilities."