The average hourly pay for women at companies such as Virgin Money and easyJet is more than 33% lower than for male staff, new figures show.
More than 500 organisations with 250 or more workers have so far published their gender pay gap figures, which reveal the difference in the average pay and bonuses for female and male employees.
For easyJet, the mean hourly rate for women was 52% lower than for men, while the figure stood at 33% lower at Virgin Money.
Both firms said men and women in the same roles were paid the same, and put the gender pay gap down to having more men in higher-paid positions.
At airline easyJet, for example, just 6% of its pilots - who earn an average salary of £92,400 - are women, while females make up 69% of its cabin crew, earning £24,800 on average.
The firm said it was actively seeking to recruit more female pilots, with a target of 20% of new entrant pilots being women by 2020.
Virgin Money said it was aiming to achieve a 50:50 gender balance by 2020 as it revealed that just 35% of employees in the highest paid quartile were women, compared to 73% in the lowest quartile.
Ladbrokes’ mean hourly rate was 15% lower for women, but that was due to the large disparity in bonus pay at senior levels, where women’s bonus pay is 25% lower (median). This meant that the firm’s median hourly rate was 2.5% lower than that of their male counterparts.
Ladbrokes Coral Group said the gender pay gap was "largely a function of weak representation at our senior levels", and said it was looking to improve gender representation.
The BBC reported its mean hourly rate for women was 10.7% lower than for men, while the figure was 30% lower for the Co-operative Bank.
Steven Pickering, chief risk officer at the Co-operative Bank, said: "Like many banks, our gender profile means that we have a pay gap which reflects the number of men in senior roles compared to the number of women.
"Through our five-point action plan, we aim to achieve a material increase in the number of women in senior roles, which, in turn, will help reduce our gender pay gap."
The Government has made it mandatory for all organisations with 250 or more workers to report annually on their gender pay gap, and are required to publish the first set of data by April.
The gender pay gap is different to "equal pay", which deals with the pay differences between men and women who carry out the same jobs.
Several of the organisations to have already published their figures reported low or no gender pay gap, including the British Museum (0%) and the UK Armed Forces (0.9%).
Cambridgeshire Police revealed women had a mean hourly pay of 13% more than men.