The government has rejected businesses pleas to delay regulations that will allow around 4.5 million employees to request flexible working hours, meaning that employers have less than eight months to prepare for the change.

Under plans released by the Department For Business, parents with children up to the age of 16 would have the right to ask their employers for flexible working hours from April, 2009. At present this option is limited to those who have children up to the age of six.

The Department believes that businesses would have “sufficient time” to cope with the changes

The government’s decision will be seen as a victory for unions over employers, who accused the government of failing to understand the economic pressures companies face.

The CBI lobbied for the introduction of the new rights to be delayed until October 2009, while some employers’ groups suggested a 2010 implementation date.

David Frost, director general of the British Chambers of Commerce, said: “I just don’t think this sends out the right message. The government has to have an understanding of the climate that we’re in – let’s see how the labour market pans out over the next year and then look at it.”

David Yeandle, head of employment policy at the EEF manufacturers’ body, said: “The last thing we need at this stage in the economic cycle is to be adding more burdens on business.”

Ministers have attempted to soften the blow to businesses by offering to waive the requirement for employers to confirm in writing the agreements to let employees work part-time, a measure that officials estimate will save employers £28m a year.

Over a quarter of a million employees will change their working hours as a result of the new regulations, according to the government’s forecasts.