All men kill the thing they love,” wrote Oscar Wilde in The Ballad of Reading Gaol, ruminating on a fellow inmate who had murdered a woman in her bed. Love is also used by Othello to justify the same crime. He asks to be remembered as “one that loved not wisely but too well” and claims: “For naught I did in hate, but all in honour.”

So how much has changed in 400 years? Even now, says Harriet Harman, the Deputy Prime Minister, “A man can say, ‘It was only because I loved her. It’s her fault I killed her. She must have provoked me. I killed her because she was planning to leave me’.” As a result, they can sometimes get the charge reduced from murder to manslaughter, with a far shorter sentence.

Between one and two women a week in Britain are killed by their partners. This is often prompted by jealousy, or as a punishment for wives or girlfriends seeking their independence.

Only last week, Neil Ellerbeck, a banker whose wife wanted to leave him, was let off with manslaughter after strangling her. The judge branded him as an “obsessive and jealous” husband who would stop at nothing to prevent his wife divorcing him. He could be out of prison in as little as three years.

In September, Brian Lewis, 31, was found guilty of murdering his wife Hayley Jones, 26, after she changed her status from “married” to “single” on her Facebook profile. She was stabbed and strangled.

“Till death do us part” is the vow we make in the marriage ceremony, but men are much more inclined than women to try to bring it forward. They are three to four times more likely than women to kill their partner or ex-partner. And of the women who do kill their husband or lover, the overwhelming majority do so after suffering years of violent abuse.

Martin Daly and Margo Wilson are evolutionary psychologists who specialise in the roots of male violence against women. In their fabulously titled The Man Who Mistook His Wife for a Chattel, they write: “Men lay claim to particular women as songbirds lay claim to territories, as lions lay claim to a kill, or as people of both sexes lay claim to valuables.” Not only do men see their partners as their property, apparently, but they have a sense of entitlement to them and therefore a huge sense of grievance at the prospect of losing them to somebody else.

Daly and Wilson put this down to the asymmetrical risk of cuckoldry. Men can’t know for sure whether their partner’s baby is theirs. With women there is no such uncertainty. So males of most species go in for “mate-guarding” to ensure that their partners can’t get pregnant by another male. And as Matt Ridley, the evolutionary science writer, puts it: “Spouse killing is an extreme form of mate-guarding.”

This can take many forms. In 2007 Susan Goswell, 63, was stabbed to death by her depressive husband Roger, 66, when he discovered that she had not been a virgin on her wedding day 46 years earlier, an inquest in Chichester heard.

Women get jealous too, of course, but evolutionary psychologists say that the nature of male and female jealousy is different. For a man it is sexual: he doesn’t want another man to impregnate his partner. For a woman it is emotional: she doesn’t want her partner to give time, attention or resources to another woman, as she needs these for raising her own family. But while jealous women will sometimes take revenge on their partners, they are more likely to take a knife to their suits than to their throats.

Daly and Wilson, in studies of spousal homicide, have found that by far the most common motive is the man’s jealousy. Sometimes this is “morbid jealousy”, in which the man becomes completely obsessed with the idea that his wife is being unfaithful, even when there is no evidence for it. Sometimes, though, it is standard jealousy, set off by her wanting to leave him. Then, says the psychologist Oliver James: “There’s a point at which, if I can’t have her, no one else will. In a kind of way you’ve got her for ever if you kill her, because no one else can have her.”

Dr Elizabeth Englander, in her book Understanding Violence, cites a study of 83 cases of spousal homicide in the US: 42 cases of husbands killing wives, and 41 of wives killing husbands. None of the husband-killers had jealousy as a motive.

Women are most at risk of being killed by their partners at the time of separation or soon after. People often ask why abused women don’t just walk out of the relationship: this is why. Englander notes that the abuser often reminded his partner that if she left him, he would track her down and kill her, and sometimes their children too.

It is no idle threat. In a Chicago study, three quarters of women who were killed had left or tried to end the relationship in the previous year. And violence that continues after separation tends to be more serious and obsessive, often including stalking and sometimes leading to murder. Women don’t tend to pursue their partners after a relationship has broken up. Men do: they are ten times more likely than women to kill partners who have left them.

And when they do, it is usually more violent than other murders. The majority of men who kill their wives or girlfriends use repeated blows or stabbings — far more violence than is necessary to cause death. This is rarely true when women kill.

So what is the mechanism that makes all this anger and jealousy explode into extreme violence against women? Men are in any case much more violent than women, and they commit many more murders. Men tend to externalise their anger, while women internalise it. Just look at disturbed adolescents: young men will fight, drink and take drugs, while young women will self-harm and starve themselves.

Tom Fahy is a professor at the Institute of Psychiatry, King’s College London. Jealousy, he says, “is a dangerous emotion, especially if it reaches pathological proportions and if there is alcohol involved”.

Although women can suffer it too, “the type of extreme, inflexible attitude, the sense of feeling of ownership, is much more part of the male psyche”. And men who are left by their partners can feel a sense of complete abandonment. When it’s for another man, “that’s a killer blow to self-esteem”.

Women who kill are already much more dysfunctional than the men who do so. “They often have a background of horrendous physical and sexual abuse themselves,” says Fahy. “They are much farther away from the mean than the average male killer.”

But do jealous men who kill their partners get an easier ride from the law? Historically, that’s been the case. In 1706, in the Mawgridge case here in Britain, it was declared that “jealousy is the rage of man and adultery is the highest invasion of property”.

Several American states used to have statutes that allowed men to kill adulterous wives without fear of prosecution — these were abolished only in the 1970s, and juries still sometimes acquit men who do.

When Harriet Harman became Solicitor General in 2001, she was horrified by the number of cases in which male killers pleaded their wives’ infidelity as provocation and had the charge reduced from murder to manslaughter. On behalf of bereaved relatives, she sent three cases to the Court of Appeal because the sentences seemed unduly lenient.

In one, a solicitor’s wife had admitted to having feelings for a karate instructor. The husband went out, bought a knife and stabbed her to death in front of their four children. Despite the apparent premeditation, he got off with manslaughter. “The relatives of the woman killed were heartbroken,” recalls Harman. “She was being blamed for her own death and she didn’t have the chance to defend herself in court. They thought the injustice of it was absolutely overwhelming.”

The Court of Appeal said that the law needed to be changed. As a result, the Coroners and Justice Bill, which is now wending its way through the House of Lords, will remove any defence of infidelity as provocation.

Not all lawyers, even feminist ones, are sure that this is the answer, though. Baroness Kennedy, a senior barrister who has spent much of her career standing up for victims of domestic violence, thinks that it’s more important for attitudes to change. “There are still ideas that somehow there are ‘good’ women and there are women who bring this stuff on their own heads. I still hear people saying that being a wicked-tongued woman is equivalent to a man being violent.”

She thinks that it would be unfair not to acknowledge in law the devastating effect that fear of abandonment has on a man. “I’d be cautious about denying to men the possibility that you could snap when you think your life is falling apart, though the defence shouldn’t be applied too generously. Changing the law is a simplistic solution to problems that ... require bigger shifts in society.”

Harman agrees that the problem is profound. “It’s about whether or not male ownership of a woman’s sexuality entitles him to take violent action. It’s very primeval.”

But surely we’ve moved on from our caveman days? Harman certainly thinks so. “Violence within a relationship is criminal, just as it is outside a relationship. We don’t accept a man’s ownership of a woman’s sexuality. It’s hers and doesn’t belong to him. It’s not for him to control her or her sexuality by violence or any other means.”

Society has already agreed that domestic violence is unacceptable, and there are no excuses for it. The men who receive sentences of a few years for manslaughter would be sent to jail for longer if their partners had survived and they were convicted instead of grievous bodily harm, for which there is no defence of provocation.

Even Othello decides that a fitting sentence is to stab himself to death. And Oscar Wilde’s protagonist? “The man had killed the thing he loved, And so he had to die.” Britain no longer has the death penalty, but at least now, once the law is changed, men who kill their partners will no longer be able to get away with murder.