Helen Corden of Pinsent Masons, the law firm behind Out-Law.com, said she believes many employers may be delaying the publication of their latest GPG data until the last minute because of fear for how their figures may be perceived.
Under the GPG reporting regulations, which came into force in April 2017, private and voluntary sector organisations with 250 employees or more are required to publish GPG data for their organisation. Similar requirements apply to public sector employers.
Employers subject to the GPG regulations are required to publish their overall mean and median pay gaps based on gross hourly pay for men and women, expressed as a percentage; as well as their mean and median gender bonus gaps. They are also required to publish the proportion of male and female employees within each quartile of their pay distribution, ordered from lowest to highest pay, as well as the proportion of both men and women that have been paid a bonus in the preceding 12 month period.
Employers are encouraged, although not required, to publish additional narrative information alongside the figures.
Employers must publish updated GPG reports by 4 April 2019, based on figures as at 5 April 2018. However, analysis carried out by the BBC found that, as of the morning of 27 March, just 37% of the UK's employers obliged to report their GPG have done so for the current reporting year.
More than 11,000 employers are expected to report their GPG this year, but the BBC said that fewer than 4,000 of the businesses have published their updated data despite the approaching deadline to do so.
Corden said: "I suspect that many companies are leaving it as late as possible to publish their gaps as either the gaps have not moved or they have gone up and they are deliberating on how to present this with minimal publicity."
"The fact that gaps have not moved or have gone up show that there is no quick fix to closing the gaps and what companies must focus on is their action plans to bring about lasting and sustainable change for ensuring that everyone reaches their full potential and women can reach the more senior positions in organisations," she said.
Last month the government released guidance aimed at helping employers close the GPG. It also confirmed earlier this year that it is not planning to make any changes to the GPG reporting rules, despite a committee of MPs recommending a number of enhancements and extensions.