One of my most high-powered female friends asked for a rise last week. It made her feel physically sick. This is a woman who confidently pitches for business in international boardrooms. But had it not been for assiduous prepping from her husband the night before, and the thought of having to face him afterwards, she might never have had the guts to walk into her boss’s office. It still makes her cringe just to think about it – even though she got exactly what she asked for.

Is she unusual? I doubt it. I long to ask for a pay rise. But it never feels like the right time. It seems pushy. It might put my boss in a difficult position – and what would that do to our relationship? In a multitude of jobs in different sectors, I have only once mustered the nerve. Which basically consisted of a breathless monologue detailing my failings, until the dear man leant forward and said: “Maybe you should do what men do – tell me why you’re worth it.” Gulp.

I tell these two rather weedy stories because of the latest figures on the pay gap between men and women. The Chartered Management Institute and a group called Remuneration Economics have found that the pay gap between male and female managers in Britain is 12 per cent, rising to a staggering 23 per cent at director level. Their survey is pretty robust: the 42,000 men and women it compares may not be doing exactly the same jobs as one another, but they do have the same job titles. And they have produced the same annual survey for years. So their finding that the pay gap has actually started to widen, for the first time in a decade, is important.

Predictable claims of male conspiracy, however, don’t sound quite right. For the same survey shows that women are being promoted faster than men – mostly by men. The average female team leader is, at 37, five years younger than her male counterpart. The average female director is four years younger. In fact, the CMI says that this could partly explain the widening of the pay gap. For a newly promoted and manager who is five years younger might plausibly start on less than a more experienced peer.

That is not to say that discrimination has disappeared. No way. I know of a hedge fund – in the vanguard of our dynamic, forward-looking economy – that recently sacked a woman for the medieval crime of getting pregnant, despite it being illegal to do so. Banks and barristers chambers in particular seem to have retained their fair share of another notorious group beginning with B. But I, and many of my friends in their thirties, cannot pretend that we have not benefited from enlightened employers who are eager to promote female talent. Yesterday I talked to a headhunter with a client who is eager to put two women on his board. That is illegal, too. But it is becoming more and more common.

Women are advancing into every corner of life. So why don’t we get paid the same? In a recent Grazia magazine survey of 5,000 people, 80 per cent of women said they felt underpaid. But, only 35 per cent of them had ever asked for a pay rise. Research in Linda Babcock’s 2004 book Women Don’t Ask: Negotiation and the Gender Divide, found that 93 per cent of female graduates from a US university simply accepted the starting salaries they were offered in their first job, while more than half of the male graduates tried to negotiate up. I was so grateful to get my first job I would never have dreamt of trying something like that.

It may sound like a cliché, but men still seem more motivated by financial reward. A few years ago, researchers at the University of Chicago paid teams of students to solve simple computer problems. Half the teams got 50 cents for each member for every problem solved; the other half got $3 per problem solved, but the cash only went to the individual who did the solving. The women performed much the same whichever group they were in. The men did 50 per cent better in the second group than the first.

When I first had to manage staff, I was amazed by how naturally some men would provide a running commentary on their achievements. The women tended to assume that their untrumpeted hard work would be rewarded: of course it wasn’t. The irony is that the women who are the best team players, who don’t like to waste anyone else’s time, who think “They’ll give me what is fair”, routinely lose out to those who shout louder. Even my (female) babysitter says: “Oh, how much is up to you.” Can you imagine a man saying that?

Our tendency to take female modesty at face value becomes a serious problem when it comes to women in caring roles. This week a whole gang of Tube drivers on £32,000 a year (mostly men) took two days off to shout about pay packages that were never under threat anyway. This left London’s nurses (mostly women), teachers (mostly women) and carers (mostly women) to walk miles to the types of work that financially we value less. That is a kind of discrimination no less heinous for being partly self-inflicted through silence. If we don’t do something about it soon, we will find that no one will do that work at all.

The rest of us, perhaps, need to stop being quite so sheepish about money. Because it’s hard to negotiate when you don’t have a clue what anyone else earns. It is not that my male friends are particularly immodest. But they often seem to know much more about where they stand compared to their peers. The new research show how naive it is for women to assume that Joe, with the same job title, is on the same package. He may not be. But equally, that may not be deliberate. We have to grit our teeth and face up to the uncomfortable fact that what we don’t ask for we may not get.

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