There were three of them walking along the street in front of me.

Their skirts were short and the heels of their shoes so high they could only wobble forward by clinging on to one another. The fake tan on their wand-thin legs was almost streak-free. They must have been about 13-years-old.

Their would-be adult sophistication was endearing; a picture of guileless innocence, one step removed from childhood and the dressing-up box. Yet, by 13, too many girls are already familiar with the gauntlet they will have to run all the way to the menopause and beyond. I bet none of the trio made it home that day (or most days) without being subject to the sorts of salacious comment that girls learn early to endure.

Generations of women have suffered in silence, brushed such remarks aside or buried their embarrassment. But instead of the problem becoming rarer in our more equal society, it appears to have worsened.

Nor does it stop at comments. In her recently published book, Everyday Sexism, Laura Bates tells us that 33% of girls aged 13 to 17 have experienced some sort of sexual abuse. Her figures come from the NSPCC. Bates published the book following the runaway success of a website of the same name. She launched it in April 2012. By last Christmas, 50,000 women had posted their experiences, a relentless drip, drip, drip of crude suggestions, sexist comments and uninvited physical encounters.

It begs the question of why it has taken so long for women to understand that this behaviour is a way of keeping them down; of showing them their place. We saw an extreme version of it in "Twelve Years a Slave". The auction was a meat market. Naked men, women and children were squeezed and pummelled, turned this way and that. They were sized up and had their teeth checked, like horses. They were spoken of as if they were dumb beasts.

The treatment was meant to be dehumanising. It robbed the slaves of status and demeaned them in their own eyes. Isn't that what we permit, to a lesser degree, to happen to girls and women in our society? Women and girls are judged, graded, marked and, all too often, groped. Isn't this just a subtler exercise of power?

Women from all over the world have written about their experiences on the Everyday Sexism website. It's as though an invisible curtain has been ripped aside to reveal something vile. The volume of correspondence illuminates covert sleaze that, for generations, has been passed over as "just a bit of fun".

More importantly, it demonstrates that what my generation saw as isolated incidents particular to us was nothing of the kind. It is pan- generational and pan-global: it's the common experience of most girls growing into adulthood. I remember how I would go home after a verbal or physical assault and check if my clothes were provocative or if somehow I "looked cheap". Reading Everyday Sexism, it's plain that what women wear and how women walk is irrelevant.

The abuse is widespread. It's about gender, not dress code or looks. It's about power and keeping women down. Just being female makes you fair game.

Sexual innuendo precedes puberty and girls absorb the message. They begin to see themselves as objects and to feel the need to be attractive objects.

Why else would a 14-year-old schoolgirl say: "If you don't have a thigh gap you need to get a thigh gap."

Why would 87% of teenage girls be unhappy with their body shape or girls as young as five worry about their weight?

More shocking is that, in 2014, teenagers talk about "studs and sluts". Boys surveyed by Zero Tolerance brag that they "want sex" or they will "move on". However, if a girl agrees to sex she may be called a slut; and by other girls.

It is a confusing picture. Too many girls are conditioned to think of themselves as sexual objects, inferior to men and designed to please. They are left walking a reputational tightrope.

And that attitude is inculcated one day at a time, one sexist comment at a time. A school teacher quoted in the book says: "There is an underlying violent and vicious attitude towards girls, a leaning towards seeing them as products to be used."

What happens to these young girls matters to society because they are the future.

As one who lived through the dawn of feminism, I was feeling mildly complacent until I read this book. Stupidly, I thought we lived in a more or less equal society. Yes, I know the figures for women MPs are shocking. And, yes, I find it depressing that Alex Salmond pats himself on the back for having 40% female representation in his cabinet when 51% of the population are female. Equality? I don't think so.

Despite these quibbles, I thought at least the principle was accepted; that it was only a matter of time until today's female graduates filled tomorrow's board rooms.

Then I ready chapter seven of Everyday Sexism. It opens with the tweet: "I'm 21 and being asked at job interviews if I'm getting married or pregnant."

What follows is depressing but known. The pay gap between men and women is 55% in the financial sector, 33% in the City of London and 14.9% in the UK as a whole.

Will girls with a subservient self-image be up to continuing the fight for equality?

Bates quotes from Slater and Gordon saying 60% of women had a male colleague behave inappropriately towards them in 2012. Last year, they said one woman in eight had left a job because of sexual harassment.

She points out in her book that, just when people were saying Jimmy Savile and others got away with workplace misconduct because things were different back then, thousands of women were posting their current experiences on Everyday Sexism. Some of them were using the same phrase: "It's just the way things are ... "

This book is a wake-up call. It is also a call to arms. There is a challenge for women because it isn't easy to speak out. Who can be bothered to chase down every crass remark and arrogant fondle? It isn't easy to confront. The difficulty is compounded if the offender is a boss, an otherwise friendly colleague or a friend of the family.

To challenge puts the victim at odds with everything women are taught about how to behave; about making life nice, about not making waves.

But it's clear to me that the uninvited sexual commentary that accompanies a girl into womanhood is a form of grooming.

Innuendo and groping are the methods. Now, too, for the young there are sexually explicit texts or photographs on the web. They speak of the perfidy of those who posted them. Mostly they speak of the continuation of a vile culture that employs "mischief" and "fun" and "pranks" in such a way that the male is always the one laughing and the girl the butt of the demeaning joke.