Britain's progress in closing the gender pay gap has shuddered to a halt and women could be waiting 100 years for equal pay.
The gap currently stands at 14.1 per cent, the same as it has been for the past two years, and at this rate could take until 2117 to close.
New data from the Office for National Statistics found that the gap is widest among women in their 50s, at 18.6 per cent.
But it has grown significantly among women in their 20s - from 1.1 per cent in 2011 to 5.5 per cent this year.
The Fawcett Society has issued the warning about the stark lack of progress ahead of Equal Pay Day today (Fri) - the day in the year when women start to work for free.
The gap is highest in London (20.7 per cent), followed by the South East at 16.3 per cent, but is falling fastest in these areas.
It is higher in the private sector, at 17.1 per cent, but has fallen by 4.3 per cent since 2011.
Sam Smethers, Fawcett Society Chief Executive, 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.
"Employers with 250 staff or more need to review their pay systems and publish their gender pay gaps, with a clear action plan in place to close it.
"All employers need to take a long hard look at their workplace culture.
"Discrimination and sexual harassment can be hidden and more common than they think.
"Proactive steps are needed to root it out and give women confidence to report it.
"Government should require employers to make every job a flexible working job, unless there is a good business reason not to.
"We also want to see a longer, more generous period of paid leave for fathers.
"This will help to address the unequal impact of caring roles which is one of the key drivers of the gap.
"For the lowest paid we need to see the Real Living Wage adopted as the minimum wage in all our workplaces. A growing number of women are trapped in the lowest paid work."