Imagine you're interviewing a 30-year-old woman for a job. She got married a year ago, and there's this enormous question in your mind. Not only do you dare not ask it – the law prevents you from asking it. So instead you think, "Great CV. Terrific personality. But I think I'd better hire the male candidate instead."

This happens in workplaces all over the country. And it happens because our system of parental leave has been based on the premise that it is mothers, not fathers, who bring up children. Employers are worried that women will take ages off work when they have babies or not come back afterwards, so they either don't hire or don't promote them. By the time a woman becomes pregnant, she is usually earning less than her partner, and it makes more sense for her to stay at home after the baby is born. If she goes back to work, she suffers the same discrimination all over again, and it becomes worse with each successive baby. No wonder women topple off the career ladder when they reach childbearing age.

So imagine if it were different. Imagine if men were just as likely to take time off as women. In one swoop, there would be much greater equality at work as well as in the home. Well, it may happen, and surprisingly the impetus is coming from a Conservative-led government.

"Flexible parental leave" sounds like one of those jargon phrases that spatter the pages of "Human Resources Weekly". But this barely noticed ingredient in the Queen's Speech will do much more for equal rights than gay marriage. It is the most powerful way both to help women at work and to ensure that the next generation is happier, healthier and more successful. The key is to allow and encourage men to be more active fathers.

We all know how well girls and young women are doing: outperforming boys and young men at school, university and in the early years of the labour market. But there is a dramatic fall-off as soon as they start to have children.

It's not what parents of either sex want. Today's young adults believe in equality. Women are used to succeeding at work and don't necessarily want to give it all up as soon as they have a baby. Men want to spend more time with their children. Both want a system that at least allows them to be equal parents if they choose to be.

All the evidence shows that this helps society too. If fathers take parental leave, their families are more likely to stay together. Even if the couple split up, the father is more likely to remain involved with his children. And the children tend to behave better, achieve more at school and have higher self-esteem. Both fathers and mothers declare themselves happier too. Meanwhile, women are less likely to fall behind at work. That's good for them and for the economy, as their talents are being properly used.

Since last year, fathers have been allowed to share much of the parental leave to which mothers are entitled. This in itself is progress; before, they were restricted to just two weeks off straight after the birth on less than the minimum wage. But the take-up has been low – only a quarter of eligible men are availing themselves of the right according to statistics out today – because the scheme has been inflexible, poorly paid and barely publicised. Most important though, none of the leave, apart from the initial fortnight, has been specifically reserved for fathers.

Experience in other countries shows that fathers don't tend to take leave if it is merely an option. When shared parental leave was introduced in Norway in the 1990s, only 2-3 per cent of men used it. Then the government reserved four weeks to be used only by fathers. That has been extended to 10 weeks, and by 2008, 90 per cent of fathers were using it.

Britain's new provisions, to be brought into law next year, haven't yet been spelled out. But it looks as if fathers will be given an extra four weeks' paid leave on top of the two weeks' paternity leave. And they will be able to share the mother's entitlement much more flexibly. For instance, both parents will be able to take time off together, which isn't allowed now. So if a mother wants to go back to work and hand the baby over to the father, she can spend a week or two showing him how it's done. And if the employer agrees, parents will be able to reduce their hours rather than deserting work altogether, or take the leave in several short blocks rather than one long one.

Ah, the employer. Whenever we talk about maternity leave or parental leave, we hear that it is terrible for business. Well, it is certainly complicated – and the Government's promise to simplify the system is welcome. But if employers want to retain their best workers, it is surely in their interest to help make it possible for work and family life to coexist.

If fathers start asking for more time off once their babies are born, that inconvenience will be entirely offset by mothers returning to work more quickly. In fact, businesses whose employees are mainly female will find these new proposals actually advantage them. And the new flexibility should help employers too.

We heard the same complaints when Labour introduced the right for parents of young children to request flexible working. Yet it has been accommodated with the minimum of hassle in the vast majority of cases. If anything, employers have found that staff who are allowed to work flexibly are more productive and less likely to leave.

Next year's legislation will extend this right to all employees. Together with flexible parental leave, it should eventually change the working culture so that fathers are no more embarrassed than mothers to ask for time off or for different hours when they have family responsibilities. Almost all of us will go through a period of working life when, as parents, we need some accommodation. It won't just be women.