Image copyright PA

Large firms will have to reveal differences between average pay for male and female workers under a change to a law passing through Parliament.

Firms with more than 250 employees that don't comply with the new rules could face fines of up to £5,000.

Large firms employ more than 10m people in the UK. Just five have published gender pay figures under the current, voluntary approach.

The Liberal Democrats had pushed for the policy despite Tory opposition.

Equalities Minister Jo Swinson (Lib Dem) said it was "fantastic news" that her party had won the "argument in government".

A government spokesman said the gender pay gap was "at its lowest ever", adding that the current rules had led to "over 275 companies, covering over 2.5 million employees, committing to analyse and take action on gender equality in the workforce".

'Valued and rewarded'

Deputy Prime Minister Nick Clegg said: "The labour market is still stacked against women. It's simply not acceptable, in the 21st century, that women on average still receive a smaller pay packet than men."

Image copyright Getty Images Image caption Liberal Democrat equalities minister Jo Swinson said the amendment was "fantastic news"

"These measures will shine a light on a company's policy so that women can rightly challenge their employer where they are not being properly valued and rewarded," he added.

The measure will be debated in the House of Lords on Wednesday, with the government tabling an amendment to the Small Business Bill.

The bill is likely to come into force within the next 12 months.

Labour shadow equalities minister Gloria De Piero said: "This is fantastic news for women but why have they waited so long?... The reality is that it's only when the government realised they would be defeated on this issue by Labour in the House of Lords that they saw the need to act."

In November official figures suggested that the gender pay gap had shrunk to a record low.