New paternity leave rules affecting men come into force
New paternity leave rules have come into effect meaning that parents will be legally entitled to share time off work during their baby's first year.
The move means parents could take six months off work each.
The government hopes to extend the measures with a fully flexible system of shared parental leave in 2015.
However, the Federation of Small Businesses said a one-size-fits-all approach did not work and added to the administrative burden on small firms.
A survey of 1,300 firms by the British Chambers of Commerce (BCC) showed that over half believed giving extra paternity leave to fathers would be detrimental.
Earlier this year Deputy Prime Minister Nick Clegg outlined plans to press ahead with changes, first proposed by the previous government.
The new rules mean a man will gain the right to additional paternity leave and pay. The rules also cover adoption.
Additional paternity leave (APL) will allow an employee to take up to 26 weeks' leave to care for the child, on top of two weeks of ordinary paternity leave.
This can only be taken 20 or more weeks after the child's birth or placement for adoption, and once the mother has returned to work from statutory maternity or adoption leave or ended her entitlement.
The rate is £128.73 a week, or 90% of average weekly earnings if that is less.
To qualify, the father must have been on a continuous contract with his employer for at least 26 weeks by the end of the 15th week before the baby is due.
The BCC said the paternity leave rules, coming into force at the same time as the phasing out of the default retirement age, were too much to cope with.
Director general David Frost said: "In the face of promises by the government to listen to the needs of business and cut red tape, these two new pieces of employment regulation will hit businesses hard."
The default retirement age means people are no longer expected to leave their posts by the current retirement age of 65 for men and 60 for women.
The TUC general secretary, Brendan Barber, welcomed the change to paternity leave.
He said: "Good employers should have nothing to fear from these employment changes, which have been consulted on extensively over the last few years."