Click here to see the statistics from power suits to pinnies

Women can be impossible. For years they fought for the right to have their home-made cupcakes with the children and go out to work. They not only wanted to be treated in the same way as their male colleagues in the office, they wanted to have more time to bond with their babies at home.

Finally the Government complied. While in America mothers still only get three months unpaid maternity leave, British mothers will soon receive a year's paid leave. What a coup. Not only that, mothers can ask for flexible hours until their children are 16 so that they can be back in time to burn the fishfingers and still expect the same promotion as their male counterparts.

So why are women complaining? According to Nicola Brewer, chief executive of the Equalities and Human Rights Commission, these new maternity benefits have actually been a disaster. Companies are never going to employ a plump 30-year-old woman wearing a baggy jumper just in case she might be about to announce the happy news of her impending twins. Sir Alan Sugar was blunt about it in an interview he gave to Rachel Sylvester and me this year. “If someone comes to an interview and you think to yourself that there is a possibility that she might have a child and therefore take time off, it is a psychological negative thought,” he told us.

The evidence seems to bear this out; women have started swapping their pinstripes for their pinnies. According to Pricewaterhouse- Coopers, there has been a 40 per cent drop in women in senior management roles at UK FTSE 350 companies between 2002 and 2007. A Grant Thornton study showed that only 64 per cent of UK firms now have at least one woman in a top-level role, compared with 91 per cent in China. Girls may be higher achievers at school and more driven in their twenties but by the time they reach their forties they are being judged more on risotto than results.

A century of women's lib appears to have been negated; maybe it would be kinder to teach our daughters to sew, play the piano and cook, to help them to enjoy their home-making careers. Or maybe the concept of a glass ceiling is as old-fashioned as a chastity belt. Some employers may not be employing “women of a certain age” any more, but increasingly it is women who are deciding they don't want to work flat out once they have had children. They are redefining themselves as mothers who work rather than career women who happen to have children.

The British Household Panel Survey, which involved 3,800 couples over eight years, found that women with part-time jobs were the happiest. They reported greater job satisfaction than those in full-time work and appeared more content than those with no job. By contrast, 78 per cent of fathers said that they were happiest working full-time.

Those shoulder-padded woman who used their stilettos to become prime ministers, QCs and consultants in the 1980s and dictated their briefs while they were giving birth now seem as old-fashioned as their big hair. The number of women in full-time professional and managerial roles peaked in 2001 in Britain. The number of married mothers working full time and with infant-age children has fallen by 6 per cent in five years across all educational levels.

The commission's answer is to demand more leave for men so that they can bear more of the domestic load. But a quarter of fathers already take less than half of their paternity leave. According to a study by Cambridge University the average man spends eight hours on cleaning, cooking and childcare per week while women spend 23 hours on domestic work. But when women were asked if they wanted their partner to take over more of the childcare, 70 per cent said no.

This doesn't mean that women have given up on their ambitions in favour of puréeing baby food. For many women, setting up their own company or going freelance so they can manage their own time has been the answer. The number of women setting up companies increased by 10 per cent in the past six months. As Sahar Hashemi, co-founder of the Coffee Republic chain, says: “A lot of women are walking away from corporations because they want to live and work differently, not because anyone is forcing them out.”

It is the old-fashioned businesses that will suffer. Good companies know that it makes sense to woo older women, even if it means creating new posts for them or allowing them to work flexitime. Women need to understand that if they take a year's maternity leave they cannot automatically expect to have received a career promotion in their absence or be able to take off every half term, school outing and holiday. Both companies and women have to realise they can't have it all - but with a bit more flexibility they can have a bigger slice of it.