There are still too many old fashioned businesses that operate as if men were the breadwinners and women the housewives

Trade and Industry Secretary Patricia Hewitt

But parents will have the right to go to a tribunal if their employers turn down their requests.

Ms Hewitt told the BBC that the government was trying to achieve a "cultural revolution in the workplace" with the legislation, due to come into force by April 2003.

She said: "It is not the government's job to tell parents how to lead their lives.

"But it is our job to provide them with more choice."

"There are still too many old fashioned businesses that operate as if men were the breadwinners and women the housewives."

Ministers believe up to half-a-million people could take advantage of the new rights.

Some say the proposals do not go far enough as employers will be able to turn down parents' requests if they show this would damage business.

The move follows cases that have highlighted the problems faced by parents who find work hours clash with childcare responsibilities.

On Monday, former police constable Michelle Chew, 36, won her sex discrimination battle against Avon and Somerset Police after they refused her request not to work shifts so she could care for her two young children.

Written requests

The new legal standards follow a government Task force report on part-time and flexible hours.

Under the new guidelines, employees request flexible working hours in writing followed by a meeting.

If the employer refuses the request the business reason must be explained in writing.

Around 3.8m parents will be able to apply for new working arrangements, 2.1m men and 1.5m women with children aged under 6, plus 200,000 parents with disabled children up to the age of 18.

Arrangements for flexible working can continue after these birthdays if they suit the parent and employer.

Mixed response

But the guidelines have had a mixed response among unions, campaign groups and business organisations.

Bill Morris, leader of the Transport and General Workers (T&G) union, said the proposals did not go far enough.

"This is still a small crawl to justice rather than a sprint towards equality.

"You still have to ask rather than exercise your right. The employer still has the opportunity to say no".

Michelle Chew: "Relieved" that three-year battle is over

The National Family and Parenting Institute (NFPI) has welcomed the plans.

Chief executive Mary MacLeod said: "Giving mothers and fathers the right to ask for flexible working hours is a big step in the right direction".

Stephen Burke, director of national childcare charity Daycare Trust, gave the measures a cautious welcome.

He said: "The government clearly recognises the needs of parents and the daily struggle they face balancing work and family life.

"But that struggle will continue until much more is invested in childcare and while most employers fail to follow family friendly working."

Business fears

But the British Chamber of Commerce has warned employers will need government support if the guidelines are to be met.

It would be "disastrous" if the changes led to more employment tribunal disputes, said BCC director general David Lennan.

The Institute of Directors fears the changes could breed resentment among co-workers who do not have families.

Miss Chew, 36, a single parent from Taunton, had wanted to work the same days each week to enable her two children to go to nursery.

The tribunal ruled the force had breached the 1975 Sex Discrimination Act because women were more likely to be looking after children.