Only one in four employers studies gender pay differences among their staff, new research has shown.
A survey of 1,000 employers found that larger firms were more likely to analyse the pay of men and women.
The Chartered Institute of Personnel and Development said its study showed firms were uncertain about the timescale for planned regulations on gender pay reporting.
Dianah Worman, diversity adviser for the CIPD, said: "We're not convinced that the proposals to publish pay gap league tables across economic sectors will be helpful in levering systemic change.
"While at first sight they might appear to be a useful sanction, they could have the unintended consequence of compromising greater transparency and be subject to misinterpretation of commitment to change if not especially if they are not set in context."
Kamaljeet Jandu, equality officer of the GMB union, said: "The campaign for equal pay between men and women has included picketing, demonstrations, legal challenges, individual cases, commissions, task forces, new policies, increased women on boards, T-shirts and a Hollywood film.
"Yet little has changed for women."
A Government spokesman said: "The gender pay gap has been falling almost continuously, is at the lowest on record and has been virtually eliminated for women under 40 working full-time.
"But we are clear that any gap is too great and that's why this Government is doing more than ever before to close it for good."