A quarter of private sector firms believe equal pay audits are "unnecessary", according to research by Personnel Today's sister publication Industrial Relations Services (IRS).
Of 103 employers polled by IRS, 24% said salary structures that rewarded workers fairly regardless of their gender were attainable without formal audits.
Reluctance to carry out equal pay reviews is widespread, the survey found, with six in 10 firms insisting they should not be mandatory for private sector employers.
Report author Noelle Murphy said: "The right to equal pay for equal work for men and women is enshrined in law through the Equal Pay Act.
"However, our research indicates that not all employees are enjoying equal pay for work of equal value. Worryingly, employers do not seem motivated to proactively address pay inequality within their organisations."
Even so, three-quarters of the 103 employers surveyed had made some effort on the equal pay front, albeit mostly on an informal basis.
Of those firms that had undertaken audits, two-thirds (69%) found that men were being paid more than women for work of equal value within their organisation. But among employers where pay inequalities were detected, there was little evidence of organisations doing anything to redress the balance.
Harriet Harman's Equality Bill, expected to be introduced to Parliament next year, will put new burdens on public sector employers - and private firms bidding for state contracts - to identify and close gender pay gaps. But it stops short of forcing all private firms to conduct equal pay audits.