The gender pay gap is widening for some women and it will now take 100 years to close it, a campaign group has warned.

The Fawcett Society said younger women as well as older female employees were now seeing their pay fall behind that of men, claiming that the drive to equalise pay is “going backwards.”

Earlier this month the society named November 10 as Equal Pay Day – a symbolic date in the year when women start to work for free because of the difference in the pay of men and women.

The date has not changed for three years, showing the lack of progress, said the society.

Chief executive Sam Smethers said: “The pay gap is widest for older women as it grows over our working lives, but we are now seeing a widening of the pay gap for younger women too, which suggests we are going backwards and that is extremely worrying.

“At a time when we are breaking the taboo of talking about sexual harassment in the workplace we need to wake up to the fact that a culture which tolerates or even fosters sexual harassment isn’t going to pay women properly either, and we know that younger women are particularly likely to experience harassment.”

Official figures show that the gender pay gap based on median hourly earnings for full-time employees fell to 9.1 per cent from 9.4 per cent in 2016, but for full and part-time workers the figure increased by 0.2 per cent to 18.4 per cent.

The gap is wider for women in their 50s, at 18.6 per cent, but has significantly grown among women in their 20s – from 1.1 per cent in 2011 to 5.5 per cent this year, said the society.

More than half of female workers admit to feeling financially unprepared for their retirement as evidence emerges of a gender savings gap, according to research by financial advice firm Close Brothers and the Pensions and Lifetime Savings Association.

The study found that 51 per cent of female workers feel financially unprepared, compared with around a third (35 per cent) of male workers.

In 183 out of 206 local authority areas, men in full time jobs earn more on average than women, but the gap varies from place to place.

In Cheshire West and Chester men earn £2.31 per hour more than women. The gender pay gap here is 16.1 per cent and is equivalent to women working unpaid from November 2.

A study by jobs site Adzuna named Chester as the most “sexist” city in the UK, with women being paid an average of £25,000 a year compared with £38,000 for men.

Although the top 10 includes the City of London and Tower Hamlets, which contains the financial area Canary Wharf, and other areas in the South East, including Wokingham and Windsor and Maidenhead, it is not thought the gap is necessarily highest in the areas with the most lucrative jobs.

For example, Blaenau Gwent in South Wales has the highest percentage gap between male and female full-time workers, with the average man on £14.07 an hour and average woman on £9.54, a difference of 32 per cent.

Knowsley in Merseyside, one of the most deprived areas of England, also appears in the top 10.

In Flintshire, men earn £2.13 per hour more than women with a gender pay gap of 15.7 per cent. This is equivalent to women working unpaid from November 3.

But the gap is much narrower in Wrexham where women earn £0.18 per hour more than men. The gender pay gap here is 1.4 per cent.

Lynsey Green, 40, an HR professional from Mynydd Isa, said women are at an immediate disadvantage if they want to start a family or work part-time.

She said: “As a HR professional I have personally experienced and seen many others go through huge career changes as soon as they have children.

“I would be interested in understanding what the pay gap would be for women without children compared with men. Another statistic I would love to see would be to compare women with and without children.

“I had a well paid job with a large multinational and got promoted several times. I had my first child and dropped to 28 hours per week and it was a seriously career limiting move.

“No promotions were forthcoming because nobody had vacancies within their teams for part-time people.

“Personally, I think I worked harder than ever when I had my child and I made every minute of my working day count.

“I had to leave on time so I could collect my child so my work had to be done by 5pm, but full-timers with no commitments were able to casually chat over coffee through the day knowing they could stay late at the end of the day – and of course all managers like the people who stay late, even if they don’t see they are less productive during the working day.

“I am out of that environment now. I requested voluntary redundancy and got it while I was pregnant with my second child so I went off and retrained and am now a happy HR manager with a great work-life balance and a salary befitting that of my profession.

“Look through jobs or job sites; very few are part-time and those which are don’t offer a reasonable wage or are of a professional standing. Companies will need to embrace flexible working and part-time working as that is very much what the next generation will be coming to expect.”

With women accounting for almost three-quarters of Britain’s six-million strong part-time workforce, the lack of skilled, decently-paid, part-time jobs affect women’s pay and their career prospects far more than it does men, says the TUC.

The TUC would like to see more employers paying the living wage. This would help tackle the growing scourge of in-work poverty and make big inroads into closing what it says is “the scandalous” gender pay gap.

Wales TUC national officer Julie Cook said: “In-work poverty has grown so dramatically that these workers now outnumber those in poverty without work in Wales. It remains a gross injustice that it is often women who bear the brunt of low pay.

“The living wage was created so that work can provide staff with a basic standard of living. But in places like Flintshire and Blaenau Gwent, most women working part-time are way off earning this.

“Councils and other public bodies can lead the way by becoming living wage employers themselves.

“But they also need to work with local employers and unions to use the living wage as part of a fair employment offer to tackle in-work poverty throughout Wales.”

TUC general secretary Frances O’Grady added: “The Government needs to boost pay for undervalued jobs mainly done by women, such as social care, and ministers must do more to remove barriers that stop women getting jobs in better-paid professions.”