Some parents could have more control over how and when they work under rules coming into effect.
Some parents will be able to choose how and when they work
New regulations mean parents of children under the age of six, and disabled children under 18, have the right to ask their employers for flexible working practices.
They will be able to request to change their working hours, work from home or go part-time.
But employers can refuse the request if they have a "clear business reason" for objecting.
Other new rules give fathers the right to two weeks' paid paternity leave and mothers increased maternity pay, with up to a year off in total.
Parents who adopt are given rights covering pay and leave for the first time.
WHAT THE NEW REGULATIONS MEAN
Parents of children under six, or disabled children under 18, can ask to work flexibly
Employers have eight grounds for refusing the request
Maternity pay rises by £25 to a maximum of £100 a
Paid maternity leave will go up eight weeks to 26 weeks
New fathers will have a new right to two weeks' paid paternity leave at
£100 a week
Parents who adopt will get similar rights for the first time
Campaigners like the Work-Life Balance Trust have hailed the move as a significant step towards ending Britain's long-hours culture.
But some business leaders, including the Institute of Directors, have said it will simply burden firms with more red tape.
"The extensions to family friendly policies may seem progressive but they will hurt businesses," said the IoD's head of policy Ruth Lea.
It could also cause resentment among workers with no young children, employment analysts have warned.
Some employers fear they could be open to sex discrimination claims if they refuse requests from staff to work flexibly.
It is thought the new regulations will affect more than 3.5m parents in the UK.
Trade and industry secretary Patricia Hewitt told the Financial Times she would consider extending the right to all parents - and possibly even to workers without children.
Campaigners are already warning businesses that they will face a flood of requests.
Others have said the rules are pointless as they
are simply a right to request, not to work flexibly.
Eligibility to request flexible working
A worker must have worked for the employer continuously for at least 26 weeks at the date the application is made
Applications must be made no later than two weeks before the child's sixth birthday, or 18th birthday in the case of a disabled child.
In the regulations, there are eight grounds on which employers can refuse flexible working requests.
These include claims that flexible working would create "additional costs" or have a "detrimental effect on the firm's ability to meet customer demand".