Fewer than 1% of eligible mothers and fathers took advantage of the shared parental leave system in the past year, a new report says.
A total of 8,700 new parents shared up to 50 weeks off between them, research by commercial law firm EMW showed.
The study revealed how the scheme, introduced in 2015 with the aim of helping more fathers take paid leave from work, is being "significantly underused", it was claimed.
The cultural stigma of men taking a lengthy break from work to care for their children could be a key reason for the low take-up, said the report.
Jon Taylor, of EMW, said: "Demand for the shared parental leave system remains very low, and families could be missing out by not embracing the system.
"Many new parents are unclear how the system will work for their families and careers.
"Fathers in particular could be concerned about coming across as less committed to their job if they ask for greater flexibility, deterring them from looking into it.
"Employers must take a proactive approach towards leave for new parents, not only for mothers, but fathers too.
"If an employer is seen as sympathetic to the needs of new parents, they are more likely to enjoy retention of staff."