Pharmaceutical giant GlaxoSmithKline (GSK) has been revealed as the top performing FTSE 100 business on gender equality, according to a new index.

The Equity Index 2022/23 produced by Lead 5050, a cross-industry accreditation body, ranked firms using official data on average salaries, bonuses, and pay at every level.

Among FTSE 100 employers, GlaxoSmithKline finished top after data showed the business had a very small median and mean overall pay gap, with pay more evenly spread throughout all levels of the organisation.

In second place, was IAG Cargo, a London-based subsidiary of British Airways owner IAG, while ITV was also a strong performer.

Leanne Linacre, chief executive officer of Lead5050, said: “Whilst the UK is a world leader in ensuring employers provide transparent data on gender-related pay, after years of progress, the gender pay gap for full-time workers has increased.

“At the same time, the number of job vacancies rose to a record level last year whilst the cost-of-living crisis continues to bite adversely affecting women who are having to reduce their hours of work because of the cost of childcare.

“Closing the gender pay gap would strengthen the economy as higher wages would encourage more women to either enter the labour market or extend their working hours.”

While GSK topped the FTSE 100 list, when smaller and public-sector employers are included, Registers of Scotland and Wykeham Staff Services in Spalding finished joint top.

The index used employers’ public submissions to identify their median gender pay gap, the mean gender pay gap, pay across different quartiles, and bonus payments.

Jackie Carter, professor of statistical literacy at the University of Manchester, said: “The Lead5050 Equity Index provides a comprehensive snapshot of how well employers are doing on tackling the gender pay gap.”