Prime minister-in-waiting Gordon Brown must help to remove barriers stopping fathers playing a more active role with their children, a report has said.
New fathers are currently entitled to two weeks of paternity leave
The Equal Opportunities Commission (EOC) said fathers were more likely to have requests for flexible working rejected than mothers.
It urged Mr Brown to push for an extension to the current two-week period of paternity leave.
The EOC surveyed 16,500 mothers and 12,000 fathers for the report.
It said the demand from working fathers to spend more time at home was not being met by employers.
This had left many new dads frustrated by the lack of time they could spend with their children, the report added.
Industry had been slow to adapt to the need for fathers to share the caring role with their partners, the report said.
Among men, there were big differences in the flexibility of working arrangements.
Men who worked in administrative and professional jobs were more likely to be allowed flexible shifts or time off than those in other professions, it found.
EOC chairman Jenny Watson said the past 10 years had seen "a strong government agenda" to provide support to mothers.
"They are now benefiting from 39 weeks' maternity leave and increases in statutory maternity pay," she said.
"Despite a revolution in their own attitudes towards fatherhood, men are still finding it difficult to make these aspirations a reality."
"Swift implementation" of additional paternity leave would "demonstrate that Gordon Brown's government is serious about acknowledging that fathers have a role at home, as well as at work," she added.
She said fathers should also have equal access to public services.
"For example, health visitors on home visits should include fathers as well as mothers," she said.
"Likewise, early years services must think about ways to engage both parents."
Last week, the government rejected Children's Minister Beverley Hughes' call to extend paternity leave to four weeks.
A Department for Trade and Industry spokesman said the current two-week period struck the "right balance" - and Mrs Hughes had not been setting out government policy.