The most common perception is, of course, that if the boss tells a mother that she can't shift from full-time to part-time, it's too bad. Indeed the law gives women the right to return to their jobs after maternity leave, but not the absolute right to work part-time. Nevertheless, the Sex Discrimination Act 1975 states that it counts as indirect discrimination if an employer requires a woman to work particular hours that are not justifiable.
Take the case of Annette Cowley, recently dismissed by her employer, South African Airways, for refusing to work two 16-hour shifts back-to- back because of childcare responsibilities. She claimed sex discrimination at an employment tribunal and won.
Even if the woman's boss asks her to work eight-hour days, she may have a case. Good reasons for asking to work flexibly are: if she cannot find full-time child care; she cannot afford full-time child care; she needs to be there when her children come home from school (perhaps because they have special needs); or she suffers from severe stress from working long hours (perhaps because her partner cannot share the child care).
It is not the case, though, that employers automatically have to comply with such requests. Rather, the law requires that they have a good reason for refusing. "Refusing even to consider a request would almost certainly be seen as unjustified if the matter went to an industrial tribunal," says Joanna Wade, specialist lawyer for the Maternity Alliance. "And so would having a policy of refusing part-time work or that the job is too senior."
Another invalid justification for employers refusing to negotiate working hours is the argument that "continuity is crucial". When one employer used this argument to say two receptionists couldn't job-share, the chairman of the industrial tribunal was not impressed. He said the problem could be overcome "by the simple means of a notepad".
The ideal, of course, is reaching an agreement that prevents any legal action.
"Simply being aware of these rights means both employers and employees should instigate negotiation as early as possible. For the employee, this can mean as early as being a few weeks pregnant," explains Ms Wade. "You can invite your employer to consider your request in the knowledge that he or she can't dismiss it without consideration. Most employers, after all, don't want to break the law."
A remaining concern of the Maternity Alliance, however, is that employers are still getting away with using the excuse of expense. "Employers often claim it is too costly to introduce job-share or other flexible working practices. But National Insurance costs are no higher for part-timers, and job-sharers share desks and computers."
In fact a report published last month by the Institute of Employment Studies shows that small businesses can save up to pounds 250,000 by introducing flexible working arrangements.
As a result of the report, the Department for Education and Employment is about to launch a campaign to encourage employers to make it easier for their employees to balance home and work life.