Alex Mahon, the company's female chief executive, who joined the company late previous year, said: "This number obviously makes for uncomfortable reading and I am determined to take action to address it".
Currently, men make up 66 per cent of this group.
Stephenson Harwood attributes its gender pay gap to the distribution of women and men within different types of roles across the business.
The pay gap at ITN - news provider for ITV, Channel 4 and Channel 5 - is 19.6 per cent.
This report also attempts to explain the disparity by pointing out the "large number of women in the lower two quartiles of the organisation", as well as the fact that "the majority of employees in the highest-paid quartile are men".
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Channel 4 said there was no evidence of gender bias in its pay awards.
"This report focuses on our gender pay gap, setting out the difference in average hourly pay between men and women across the organisation, as at the public authority snapshot date of 31 March 2017". The BBC's is 10.7 per cent.
Channel 4 said it was aiming for a 50:50 gender balance among its top 100 earners by 2023. The company said this was because there were "fewer women in senior bonus-eligible roles during this time period".
59% of Channel 4 employees are female and "we have a low employee turnover rate", the broadcaster said.
Channel 4 said it aims to boost career progression for women at senior levels by supporting more than 200 women over the next few years with a Women's Development Programme and undertaking independent research among female staff to understand and assess their views about their workplace.
The gender pay gap for full-time workers in London is lower than the national average at just over 16 per cent. Pearson has also made a voluntary commitment to extend gender pay reporting globally by 2020. This is because to reduce the gender pay gap to zero we would need to achieve gender parity in our lower two quartiles, which are now predominantly female (65 per cent).
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