The new legislation has received a warm welcome from industry experts and campaigners.
Sarah Williams-Gardener, director of Opportunity Now, said: "We welcome the extension and applaud the Government's progressive approach to workplace practices. Flexible working is not a burden to business.
"In challenging economic times, where salaries are being frozen and bonuses are vanishing, flexible working can offer a way of keeping talented people engaged and motivated. Enlightened employers are actually seeing flexible working as a way to retain expertise, cut overheads and motivate staff."
Since 2003, parents with children under the age of six (or 18 if the child is disabled) have had the right to request flexible working and from 2007 carers of adults were also given the right. But the Government has been committed to this latest change since May 2008 and when Peter Mandelson became business secretary fears surfaced that the proposals might be put on hold.
Stephen Beynon, managing director of ntl:Telewest Business, said: "Undoubtedly there will be a mixed response from businesses to the news more employees will have the right to request flexibility. But this sense of trepidation is unfounded. Flexible working can help reduce costs and improve employee efficiency."
He added: "Just like the markets they operate in, businesses are no longer static. Their business models must reflect this. Forward-looking businesses will see this as an opportunity rather than a burden."
But Kathleen Healy, partner in the employment, pensions and benefits practice at Freshfields, warned: "When deciding whether to allow an employee to work flexibly, employers may be reluctant to accommodate someone with a teenage child than someone with, for example, a young baby, as they may feel the person's needs are less pressing. Remember that this will not be an acceptable justification. The decision must be based purely on objective business grounds, and not on employees' personal circumstances."