New league tables will also be launched giving details of companies failing to address the problem.
And ministers are taking action to make sure that thousands more girls study maths, engineering, science and technology at school.
Women and equalities minister Nicky Morgan said the Government wanted to secure “real equality” for women and reduce the gap in pay between men and women.
“In recent years we’ve seen the best employers make ground-breaking strides in tackling gender inequality.
“But the job won’t be complete until we see the talents of women and men recognised equally and fairly in every workplace.
“That’s why I am announcing a raft of measures to support women in their careers from the classroom to the boardroom, leaving nowhere for gender inequality to hide.
“At the same time I’m calling on women across Britain to use their position as employees and consumers to demand more from businesses, ensuring their talents are given the recognition and reward they deserve.”
A £500,000 package was announced aimed at helping the 8,000 employers who will have to publish their average pay and bonus gap between men and women.
The first league table will be published in 2018, making it possible for women to compare pay in different sectors.
The Government said it aimed to have 15,000 more girls studying maths and sciences by 2020, a 20% increase on current numbers.
TUC general secretary Frances O’Grady said: “If David Cameron is serious about ending the gender pay gap within a generation we need a much bolder approach from ministers.
“While today’s announcement is a step in the right direction, we’re disappointed that firms won’t have to publish their gender pay gap figures until 2018.
“It is a real shame that bosses won’t be made to explain why pay gaps exist in their workplaces and what action they will take to narrow them.”
The TUC said it was “shocking” that the gender pay gap was still over 19% for all workers and 9.4% for full-time employees, adding that at the current rate of progress it would take almost 50 years to close it.
Chris Benson from law firm Leigh Day said: “The Government has finally woken up to the fact that the gender pay gap stubbornly persists, despite over 40 years of unequal pay being illegal, and recognised that steps need to be taken to minimise or remove that gap.”
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