Two in five people are unaware of new rights allowing them flexible working arrangements to help with childcare.
And many do not believe their boss will respond positively to those rights, new research revealed today.
More than half of working men have no knowledge of the new law coming into force on April 6, which will give parents of children under the age of six or of disabled children under the age of 18, the right to request flexible working.
The Equal Opportunities Commission (EOC) said its survey of 800 people showed the public needed more information about the new rights, which will affect 3.7 million parents.
Only one in five of those polled were fully aware of the changes but most people were strongly in favour when given details.
The law aims to give parents of young children more flexibility to juggle home and work lives by asking to start work later, share jobs or even do some work from home.
One in six of those surveyed said their bosses would probably turn down a request for flexible working but resentment from childless colleagues was less of an issue than previously thought, said the EOC.
The research was published as part of an EOC campaign to make people aware of the new law, ahead of a publicity drive by the Government.
Posters and leaflets bearing the message: "I can't carry on", will be distributed to health centres across Britain and be displayed on London Underground stations, in a bid to show that the world of work has moved on since the days of the Carry On films.
Workers in London had the least confidence that their employers would allow them to work flexibly.
Julie Mellor, chairwoman of the EOC said: "We need a radical change of culture in the workplace so that parents feel confident enough to ask their boss for flexibility if they need it.
"This must be seen as a real option for men too. Our research shows that men are less likely than women to have access to flexible working, even though they are now doing a third of parental childcare.
"Asking to change your hours isn't a sign that you're any less committed to the job."
David Frost, director general of the British Chambers of Commerce said: "Flexible working can increase staff morale and business productivity.
Many businesses recruit and retain valuable staff because they are willing to think beyond the traditional Monday to Friday, 9 to 5."
Trade and Industry Secretary Patricia Hewitt said: "This research proves how important it is to raise public awareness about the new rights, especially the new paternity rights and flexible ways of working.
"That's why we are launching a national advertising campaign later this month. It will target fathers, mothers and employers too."
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