Theresa May has vowed to tackle the "burning injustice" of the gender pay gap as the deadline arrives for the UK's largest companies to report their figures.
The Prime Minister used an article in The Telegraph to compare the pay gap to the women's suffrage campaign a century ago, saying "major injustices still hold too many women back".
Her intervention comes as time is running out for firms to publish the average pay gap between male and female workers.
All employers with more than 250 staff have been told to publish their gender pay gap by April 4, although the Press Association understands firms will still be able to submit their figures beyond the midnight deadline.
As of 8am today, nearly all of the 9,000 organisations expected to report their gender pay gap had done so.
Of the 8,874 firms to submit data so far, 78% had a gender pay gap in favour of men, while 14% reported a gap in favour of women. The remaining 8% said they had no gender gap at all.
"A hundred years ago, some women first won the right to vote," the Prime Minister says.
"But for all the welcome progress in the decades since, major injustices still hold too many women back.
"When I became Prime Minister, I committed myself to tackling the burning injustices which mar our society. One such is the gender pay gap."
While the difference in median hourly wages earned by men and women is at an historic low, Mrs May says progress is still too slow and action was needed to close the gap for good within a generation.
"It is essential that we do so. Most importantly, because equality for women is a right, and our whole society is the poorer as long as it remains unrealised," she said.
"There is also a clear economic imperative. It is estimated that if women and men enjoyed parity in their hours, pay and seniority at work then we could see up to £150 billion added to our GDP."
Mrs May said making the figures public "will make for uncomfortable reading", adding: "By making this information public, organisations will no longer have anywhere to hide.
"We will have established a baseline from which to hold them to account in the future.
"Shareholders and customers will expect to see improvements, and will be able to hold organisations to account if they fail to achieve them."
She also called on workplaces to rid themselves of "outdated stereotypes" and recognise that everyone brings their own experience into their role.