LONDON — Claire Foy, who stars on Netflix’s hit series “The Crown,” is far from the only British woman paid less than her male counterpart. New figures show that nearly 8 in 10 companies and public-sector organizations in Britain pay men more than women.

Under legislation introduced last year, all companies in Britain with more than 250 employees had until midnight Wednesday to publish data on their gender pay gaps. Different from unequal pay for equal work, the pay gap in this context is defined as the difference in the median hourly rate paid to men and women, whatever the job.

As of Thursday morning, the figures showed that 78 percent of firms paid men more than women, 14 percent paid women more than men, and eight percent said they had no gender pay gap. Overall, the data showed a 9.8 percent median pay gap.

Britain is one of the first countries in the world to introduce mandatory reporting of data on gender pay. Australia has a similar requirement. But neither country goes as far as Iceland, where the onus is on employers to prove they are paying men and women equally.

The long-standing issue of pay parity in Britain and elsewhere was highlighted, once again, last month when producers on “The Crown” revealed that Foy, who portrays Queen Elizabeth II on the series, earned less than her co-star Matt Smith, who has a supporting role as Prince Philip.

Writing in the Telegraph earlier this week, British Prime Minister Theresa May said that she was committed to “tackling the burning injustices which mar our society. One such is the gender pay gap.”

Campaigners in Britain say transparency will help to shame employers into doing more. Anyone can peruse the data and, should they wish, compare sectors -- the biggest pay gaps were in construction, finance and insurance, and education -- or even competitors. The budget airline Ryanair had a pay gap of 71.8 percent, for instance, which was much higher than its rivals.

Under the new rules, businesses will have to update their figures annually, which advocates hope will encourage them to take steps to close the gap.

About 10,000 companies filed their data to the British government’s Equality Office by Wednesday’s midnight deadline. About 1,500 failed to meet the deadline, according to the Equality and Human Rights Commission (EHRC), the watchdog that will take action if companies don’t comply within a month. Those companies could face fines.

“Reporting gender pay gaps is not optional; it is a legal requirement, as well as being the right thing to do,” said Rebecca Hilsenrath, chief executive of the EHRC. “We will soon be starting enforcement against all employers that haven't published.”

According to separate data published in 2017, the average gender pay gap in Britain stands at 18.4 percent.

Some lawmakers have been tweeting with the hashtag #paymetoo, a campaign encouraging employees to talk to co-workers about what they earn and to raise these issues in the workplace.

Amber Rudd, Britain’s home secretary who is also the minister for women and equalities, encouraged businesses to take further steps to reduce the gap.

“Closing the gender pay gap also makes economic sense. Research shows that improving women’s participation in the labor market could add £150 billion to the economy by 2025. That’s a number we cannot afford to ignore,” she said.

Sam Smethers, chief executive of the Fawcett Society, a women’s rights organization, called the reporting “a game changer.”

“It forces employers to look at themselves and understand their organizations and it prompts employees to ask some hard questions,” she said in a statement. “But even better than that, finally women are realizing that they have a right to talk about pay and they cannot be silenced.”