Government plans will force UK companies with 250 employees or more to publish their gender pay gap reports in the next year.
The new measure is part of government plans to tackle workplace discrimination.
Womens and Equalities minister Justine Greening said: “Helping women to reach their full potential isn’t only the right thing to do, it makes good economic sense.”
She added: “I am proud that the UK is championing gender equality.”
The UK gender pay gap is 18.1% for all workers and 9.4% for full-time staff. Public, private and voluntary sector firms reports on their gender pay gap will also include bonuses.
Currently, around half of the UK workforce will be affected by the new reporting rules; 9,000 employers and over 15 million employees.
Emma Codd from Deloitte UK, which already publishes its gender pay gap figures, said: “Today sees a big step forward in the journey to achieve gender parity in the UK.”
Sam Bowman from the Adam Smith Institute described the new measure as “counterproductive”.
He said: “It reinforces the idea that the gender wage gap is caused by discrimination by firms against women.”
He added: “It’s more to do with women being expected to take a lot of time out of work after having children, which interrupts their career progression. We have more of a motherhood pay gap than a gender pay gap. That gap can be closed by encouraging men to handle a more equal share of child-rearing time.”