The government has argued that the new rules have been put together in such a way as to minimise the administrative burden on employers.
It is estimated that the take-up of the additional paternity leave will be less than 6 per cent and that it will affect 0.7 per cent, or 1 in every 137, of all small businesses.
Setting out details of the regulations, Pat McFadden, the Business Minister, said that they will give families extra choice and flexibility.
Mr McFadden continued: "The number of businesses affected is expected to be small (less than 1 per cent of small businesses) and we will work with business to make sure any changes are introduced in a way that minimises burdens and gives them predictability in the provision of leave. As family friendly policies have been introduced we have seen more retention of mothers in their current jobs when they go back to work."
Harriet Harman, Minister for Women and Equality, added: "Mothers will be able to choose to transfer the last six months of their maternity leave to the father, with three months paid. This gives families radically more choice and flexibility in how they balance work and care of children, and enables fathers to play a bigger part in bringing up their children."
However, David Frost, the director general of the British Chambers of Commerce, questioned the timing of the extension.
Mr Frost commented: "There is absolutely no guarantee that businesses are going to be back to full health by 2011. This is going to be an administrative nightmare for business."
The Chartered Institute of Personnel and Development (CIPD) agreed.
Mike Emmott, the CIPD's employee relations adviser, said: "We share the widely expressed concerns about the principle of allowing parents to convert maternity leave unused by mothers into paternity leave for fathers ? we have always maintained the administrative burdens involved could cause a real headache for employers."
Mr Emmott also suggested that take-up of the scheme would be low because paternity leave paid at the statutory level is not appealing to fathers for financial reasons.
He added: "Our research shows that paid paternity leave, restricted as it is to a statutory £123.06 per week, is not attractive to the vast majority of fathers. We found that less than half of fathers would take even the existing two weeks paternity leave at statutory pay levels, many preferring to take paid leave instead. So the proposed increase in 'paid' paternity leave is unlikely to lead to any dramatic increase in take-up."
But the CIPD did say that it was pleased the government is moving towards a more equitable sharing of the burden of child support between mothers and fathers in the early months after a baby is born.
Addressing the problem of the gender pay gap, Mr Emmott concluded: "Any realistic plan to achieve this is bound to be expensive and could only be implemented over many years?
"However, without some further steps in this direction, the stated aim of all the main parties to close the gender pay gap will be hobbled in one important regard. This is a cultural issue that government cannot tackle alone. But there is a role for government, working closely with employers, to nudge cultural norms in the right direction."