First it was Hilary Mantel who dug her claws into Kate Middleton; now it's the classicist Professor Mary Beard.

Bemoaning the way women in the public eye are judged on their looks, Beard has described the Duchess of Cambridge's carefully constructed image as that of "an admirable, maternal, doll-like precious vessel".

It's not nearly as unkind as Mantel's remarks, in which she said that Middleton, "a jointed doll on which certain clothes are hung", appeared to have been "designed by a committee". Yet, mild though Beard's description is by comparison, it is still unflattering, suggesting Kate is a blank canvas on which her duties and our expectations can be projected; as, indeed, is the case.

More fascinating than Mantel's and Beard's comments, however, is that neither is likely ever to be asked on to a catwalk, and well they know it. Indeed, in Beard's case, far from intending to denigrate those more beautiful than she is, the academic is not merely defending women's right to be less than gorgeous but actively advocating they break out of the straitjacket in which public expectation confines them.

Beard, who must qualify as one of the least glamorous intellectuals to grace our TV screens since Malcolm Muggeridge, is a refreshing and inspirational media presence for those of us who squirm at the procession of Barbie dolls presenting news bulletins and games shows. We all know these immaculate young women are hanging by a thread. It's like watching Anne Boleyn and seeing the spectre of the executioner close behind, ready to swing his axe at the first hint of a dewlap or bingo-wing. Thus, while the careers of wrinklies like John Simpson, John Humphrys and David Attenborough seem only to improve with age - and nobody comments on their liver spots - most women on TV melt discreetly away in middle age, to save everyone's blushes.

Beard's comments were made ahead of a lecture she is giving on Friday on The Public Voice of Women. They coincide neatly with the revelation that the Conservative Party is not only haemorrhageing women, but excluding them. Six cabinet committees have not a single woman member, women accounting for only 14% across all such committees. Meanwhile, Hollywood has admitted it is digitally enhancing actresses without their knowledge, lengthening limbs, nipping in waists and adding expression to those who have been botoxed until they can barely blink, let alone emote.

In the face of such insane expectations of perfection, who would take on a high-profile job or batter down the door of the Tory HQ? One can blame women's lack of ambition, or the difficulties of juggling home life, childcare and a demanding career, but it seems to me that in other professions (the law, medicine, or business) many women are reaching the top and are comfortable there. The difference is they do so away from the public eye. Those who opt for politics or television subject themselves to intense scrutiny, examined under a magnifying glass as if they were specimens in a lab.

Who among us could cope with the remarks Beard has had to suffer? Only someone with great strength of mind could endure being called "too ugly for TV" with equanimity, let alone humour. Yet, sadly, it is a terrible hidden truth that, just as women's equal status is gradually acknowledged, the piranha fish of social media, gutter press and celebrity magazines are cutting the ground from beneath our feet. It would take a rhinoceros hide and armour-plated sense of self-worth willingly to enter the lion's den of trial by public ordeal, knowing full well that even those with a complexion like a peach will be picked apart.

Women, says Beard, pay a higher price than men for being in a public position. In terms of the gratuitous criticism they attract, she's right; not that I wish men were subjected to such harassment. On the contrary. The sooner the public grows less bitchy, the better for everyone. The more plain and older women are given positions in the media or in prominent jobs, the faster society will broaden its horizons. With her insistence on being herself, Beard is that rarest of beings: an academic who has stepped out of her ivory tower and who might just improve life for ordinary women as a consequence.