Male managers in the UK are earning around £11,600 ($15,700) a year on average more than their female peers, according to a new study.
The Chartered Management Institute (CMI) said the gender pay gap – which takes into account salary and bonuses, as well as car allowance and commission – was at 26.8% for the UK's 3.3 million managers.
The gap edged up slightly to 23.6% from 23.1% last year when taking managers' basic salaries alone into consideration.
New government regulations introduced in the spring demand that firms with 250 or more employees publicly disclose the size of their gender pay gap by April 2018. The law is intended to help in the fight against workplace discrimination.
However, the CMI said only 77 of the 7,850 UK companies to which the new law applies had disclosed their gender pay gap figures as of 22 September.
"Too many businesses are like 'glass pyramids' with women holding the majority of lower-paid junior roles and far fewer reaching the top," CMI chief executive Ann Francke said.
"We now see those extra perks of senior management roles are creating a gender pay gap wider than previously understood.
"The picture is worst at the top, with male CEOs cashing in bonuses six times larger than female counterparts."
The findings, which are based on a survey of nearly 120,000 employees from 432 organisations, revealed that women are far more likely to fill junior management roles compared to men.
They also showed that the pay gap widens significantly at higher level managerial positions, with men at director-level positions earning £175,673 on average per year compared to women earning £141,529.
"Our data show we need the government's gender pay gap reporting regulations more than ever before," Francke added. "Yet, less than one per cent of companies have reported so far.
"Time for more companies to step up and put plans in place to fix this issue. It's essential if UK companies are to survive and thrive in the post-Brexit world."