The gender pay gap will not be closed without legislation to make shared parental leave compulsory, according to a report on the workforce of the future by legal firm Burness Paull.

Written following a series of debates with major employers in London, Edinburgh and Aberdeen, the Future Chemistry report concludes that the UK Government will need to legislate because businesses are unlikely to act voluntarily to tackle the issue – and without new laws, the so-called "pregnancy penalty" will remain. That arises where women take time off to have children and by the time they return, their male contemporaries have progressed further in their careers.

Morag Hutchison, a partner in Burness Paull's Employment team, commented: "The root cause of the gender pay gap is biology – women take time off work to have children.

"That 'pregnancy penalty' is at the heart of the gender pay gap because when women return to work, their male contemporaries have often moved on into higher-paid positions and it is more difficult for women to progress as they often remain the primary carer. If we as a society want to truly address this issue, we need to take a long hard look at how we divvy up parenting duties."

Ms Hutchison said existing rules on shared parental leave were complex and not all parents were eligible. She added: "Much depends on the employer, and it was clear from our debates that human resources professionals believe companies won’t act alone to introduce a 'use it or lose it' system for parental leave.

"The reporting of gender pay gap figures and the 'pregnancy penalty' emphasises how UK society still has conflicting views about the role of men and women. If businesses won’t go down this route voluntarily, legislation would appear to be the only route to tackle this aspect of the gender pay gap. New laws would in effect make it compulsory for both parents to take time off work to raise their child, a system already in place in some Scandinavian jurisdictions.

"However, politicians will need pressure from society to enact such legislation, which in turn will require changes in the way society perceives the roles of parents and carers."

One female contributor to the London debate had said: "If you talk about women’s place at work without talking about who looks after the kids at home, it’s like talking about why the ground is wet without being allowed to mention the rain." 

The report also examines other major workforce issues such as tackling sexual harassment, supporting employees with mental health challenges, understanding that gender is only one issue when it comes to true diversity, and the impact of technology on the workplace of the future.

It was published to mark the statutory deadline for companies with more than 250 members of staff to publish their gender pay gap, or the difference between the average earnings of men and women.

Click here to view the report, and here for an accompanying video.