The move paves the way for an extra 4.5 million requests as rights are extended to parents of children aged up to 16. Business leaders say the move will be an employment nightmare for the UK's small businesses.

Adam Tyrell, employment chairman of the Federation of Small Businesses, said:

"The current flexible working regime seems to be working, but the Government should be cautious about extending it too far, which could be damaging to small businesses and, as a result, the millions of people they employ."

However, research by the Department for Business, Enterprise and Regulatory Reform (BERR) has revealed that small businesses are more likely than larger businesses to accept flexible working requests.

BERR minister John Hutton said:

"This is an excellent report that will give a big boost to busy parents who need more help balancing work and family life. It can also help employers who often find they get the best out of mums and dads when they allow them to work flexibly."