Why do they hate her so much?

A cornucopia of abuse has greeted Emma Nicholson's defection. Those who only read the polite press may have missed the full flavour of it. Still it continues, six days after her departure, with a bold Sun headline yesterday reading "Two-Faced Emma". The barrage has been extraordinary and disproportionate.

Alan Howarth received a pretty steaming mound of invective, accusing him of careerism, ambition, ratting, inconsistency and more. They tried to dig dirt with stories of parliamentary foreign trips with a baroness on the same committee. Nothing outrages more than betrayal, schism and defection: no holds are barred, no filth too dirty, no abuse too strong. Floor-crossers down the years, from Reg Prentice to the 30 SDP breakaways (including that remarkable double-bouncer, John Horam), all bear the scars of a flight of verbal knives hurled into their fleeing backs.

And yet no invective has sunk quite so low as that attracted by the defection of the relatively humble backbencher, Ms Nicholson. Howarth's critics implied he was, or had been, a man of substance and stature - no suggestion that he was stupid or worthless. But when Portillo called Emma Nicholson "silly", that summed up the whole sexist tone of her treatment. (His departmental colleague Nicholas Soames's intemperate assault on Princess Diana was of the same ilk.) Women get it in the neck in the Tory party, Mrs Thatcher notwithstanding.

Teresa Gorman has no reason to like Emma Nicholson. Gorman is one of those xenophobic Euro rebels Nicholson accuses of having dragged the party to the extreme right. Yet in a backhanded way, Gorman confirms the sexist treatment she thinks Nicholson has received at the hands of the party they plainly both deplore.

"She is a patrician, not really a politician," Gorman says. "However thick or daft they are, patrician Tories always get jobs in government - but not if you are a woman." She lists Lennox Boyd, Hogg, Sackville, Archie Hamilton, Waldegrave, Ancram, Soames and Maude as just a few examples of the scions of Tory dynasties who rose without question or, she implies, much merit. "They are all part of the ruling elite. It's all connections and who you are - but not if you are a woman, and that rankled with Emma because she is one of them."

Deep-dyed dislike of women in their ranks permeates the parliamentary party, and it isn't just feminist Teresa Gorman who says so. There is a bountiful supply of very able women who have tried without success to break in. Nicholson was a fighter for more women within the party and she founded the successful High Fliers recruitment initiative. That always marked her out for special mockery among her male parliamentary colleagues, for the one thing worse than a woman MP is a feminist woman MP.

The litany of sexist abuse that has been heaped on Emma Nicholson is worth detailing. John Carlisle MP described her as "a woman who has prostituted herself". Another MP said: "She's a frightful bitch". One MP mused, "Is it something to do with the menopause?" while Exeter's prospective candidate called her "The Wicked Witch of the West". Woodrow Wyatt (The Voice of Reason) called her "vain and silly".

Past-master of poison Lord Tebbit, writing in the Sun, responded tartly to her accusation that eight years ago - when she was a vice chairman of the party and he was chairman - he had rebuked her for her attempts to bring more black and Asian women into the party. He retorted: "In fact I fired her because her unrelenting demands for more office space, new curtains, furniture and staff were costing more than she was worth... No Miss Nicholson, I don't see you as a woman of political principle. I see you as a hanger-on to the coat-tails of anyone who might advance your ambition."

Lord McAlpine, former party treasurer, dredged up the worst dirt when he recalled scandal from her vice chairman days: "Emma Nicholson put a lot of noses out of joint and it was not long before her committee discovered that she was thought to be having an affair with a married man. Those women set about her like a pack of hungry wolves, and had it not been for the personal intervention of Margaret Thatcher, who took the view that the whole matter was a load of nonsense, Miss Nicholson's political career would have come to an abrupt halt."

The Daily Mail duly dispatched its terriers, who came up with an "exclusive" they could have found in the cuttings. Nicholson started a relationship with her present husband, Sir Michael Caine, when she was a vice chairman of the party and he was still married to his former wife, Janice. In these days when divorce is common, almost everyone has some aggrieved former spouse or lover whose old wounds can be gouged open again to serve a purpose, so Janice Caine was duly prodded into reliving the details of her betrayal, humiliation and desertion.

There is no such thing as a clean break in politics, but this defection must rank as one of the most bizarrely rancorous. Political parties are largely tribal, so affiliation to them is more visceral than rational. Clan loyalty and uncomprehending fear of the utterly alien terrain across the floor keeps most of them fixed immutably in their own benches.

But underneath there rankles the real worm in the Tory breast - she is a woman. Women just don't do this. Women are the little helpers and helpmeets, the secretaries and Girl Fridays of the party, running the back rooms and the constituencies, loyal as labradors, without whose devoted service the men of the party could not function. Gillian Shephard and Virginia Bottomley are unheeded tokens, patronised, belittled and ignored. "Witch", "bitch", "vain" and "silly" she may be, but what Emma did was above all unwomanly and unnatural.

Yet she has proved to be made of tough stuff, standing her ground, rebutting each sally. To each new sneer she has retaliated with more devastating stories from within the bowels of the party: once she was hit in the pit of the stomach by an MP outraged at her vote in support of the Nolan anti- sleaze measures. With chapter and verse she has denounced them all roundly as racist, chauvinist, Little Englanders, fudging their principles, and pandering to hard-faced populism. In the insult stakes, she has scarcely drawn breath, scooping up the mud and hurling it back again with far more deadly accuracy than any of the old boys lined up on the other side.