Trevor Phillips, head of the new Commission for Equality and Human Rights, has said working mothers are the most discriminated against.
Mothers and fathers have the right to paid leave
But changes contained in the Work and Families Act, due to come into force in April 2007, promise to boost the rights of mothers and fathers.
Q: What are the current rights for mothers?
Statutory Maternity Pay (SMP) is currently paid to mothers for 26 weeks.
SMP is paid at 90% of the woman's average earnings for the first six weeks and at the same rate, or else at £108.85 a week - which ever is the lower amount - for the remaining 20 weeks.
For the remaining 20 weeks, it falls to £108.85 a week - unless it is already below that figure, in which case it stays the same.
Once this is up, women meeting certain conditions are entitled to take a further 26 weeks of maternity leave - usually unpaid, unless their employer chooses to contribute.
To be eligible, they must have completed 26 weeks continuous service with their employer by the beginning of the 14th week before their expected week of childbirth.
SMP is paid by employers and then reimbursed by the Treasury.
In which ways will these rights change?
SMP will be extended to 39 weeks from 1 April.
Women will also be able to go into work for a total of 10 days during their maternity leave without losing their SMP entitlement.
The period of notice for returning to work from maternity leave will be extended to two months from the current 28 days, to make it easier for businesses to plan their staffing needs.
Q: What are the current rights for fathers?
Fathers can currently claim two weeks Statutory Paternity Pay (SPP) at £108.85 a week or 90% of their average weekly earnings - whichever is the least.
It can be taken from the date of birth or up to eight weeks from the birth.
To qualify, the man must have worked for his employer for 26 weeks by the 15th week before the baby is due and earn more than £84 a week.
He must notify his employer of the date he wants to start paternity leave in the 15th week before the baby is due.
Q: What else is in the Act?
The right to request flexible working, currently limited to parents of young children, will be extended to carers of sick or disabled people from 2007.
And SMP will be calculated on a daily rather than weekly basis, to allow mothers to work a few days while on maternity leave without losing a whole week's money.
The government aims to increase paid maternity leave again to one year by the end of the current parliament.
The Act also allows for the government to introduce a right for fathers to request up to 26 weeks unpaid paternity leave.
Q: What will be the costs for business?
The government says the cost to businesses will be "quite small" at between £25m and £70m.
It says the move will be good for business because working parents will be more productive if they are not worried about their children and less likely to leave the workforce.
The plans are backed by the Institute of Directors and the Confederation of British Industry (CBI).
The CBI says it accepts the principle of extending family friendly rights but says compensatory changes would be needed to make up for the "increasing burden" for businesses.
But there are fears the changes will hit small businesses particularly hard, especially if come under pressure to pay the full salaries of fathers on leave, as many currently do for mothers.