Women in Medway effectively went without pay for more than four months last year due to the gender pay gap, figures show.
Recently, all companies with 250 or more staff were required to report their gender pay figures, with more than three-quarters of companies nationally showing a gap in pay favouring male employees.
In Medway, Office of National Statistics figures show that women in work earned an average annual salary of £18,379 in 2018 – 40% lower than the average man’s salary of £30,729.
It means that, in effect, women in Medway worked for free from August 7 last year.
The average pay figures are calculated using a median, rather than mean, average, to stop them being skewed by particularly small or large pay packets.
The difference in pay can partly be explained by the number of women in part-time work. An estimated 18,000 women in Medway were in part-time work last year, around 38% of the female workforce.
Of the 60,000 working men, too few were in part-time work for the ONS to provide an estimate.
Women in work earned an average annual salary of £18,379 in 2018 – 40% lower than the average man’s salary of £30,729
Despite that, the difference in pay was still evident in full-time roles: men in Medway earned an average of £33,588 last year, and women £24,568 – 27% less.
Across the UK, the average gender pay gap was 36% across all roles and 18% for full-time.
The recent deadline for large companies to report their gender pay gap saw some high-profile companies demonstrate large gaps, including the airline Ryanair (64.4%), the health provider Intrahealth (57.4%) and Sheffield United football club (48.2%).
TUC general secretary Frances O'Grady said: "Big employers clearly aren't doing enough to tackle the root causes of pay inequality and working women are paying the price.
"Government needs to crank up the pressure. Companies shouldn't just be made to publish their gender pay gaps, they should be legally required to explain how they'll close them, and bosses who flout the law should be fined."
Carolyn Fairbairn, director general of the CBI, said businesses cannot close the gap by themselves, adding: "Many of the causes lie outside the workplace including a lack of affordable, high-quality childcare and better careers advice.
"Companies and the Government working together remains the best way to deliver the long-term, lasting change that's needed."
Minister for women and equalities, Penny Mordaunt, said: "Actions to tackle the gender pay gap are good for business. That's why we have produced support to help employers close their gaps.
"We recognise that in order to close the gap entirely we still need a much wider cultural change, that is why we have introduced a range of initiatives to tackle the drivers of the gap, including shared parental leave and spending around £6 billion on childcare support."