The traditional crime of passion is to be swept away in the most radical overhaul of the murder laws in 50 years.

The reforms, including a defence for people who kill when they feel “seriously wronged”, would result in life sentences for about 100 killers a year who currently escape murder convictions by claiming that they were provoked by unfaithful or nagging spouses. At the same time, people who kill because they feel seriously wronged by someone’s “words and conduct” could escape a murder conviction under a new partial defence.

The changes, outlined by ministers yesterday, will also make it easier to prosecute gang members who join in an attack that results in murder, even if they did not wield the knife.

Ministers have ruled out plans to introduce US-style categories of murder, saying that there was no consensus to proceed or to tamper with the mandatory life sentence for murder.

The changes come after years of consultation on the laws on homicide and amount to the first overhaul since the Homicide Act of 1957. They have the backing of both the Attorney-General, Baroness Scotland of Asthal, QC, and the Solicitor-General, Vera Baird, QC, and will be contained in a law reform (victims and witnesses) Bill in the next parliamentary session.

The reforms will end the use of a centuries-old defence of provocation, which enables mostly male defendants to escape murder convictions and be found guilty instead of manslaughter.

Harriet Harman, Minister for Women, said: “We want to abolish the culture of excuses that allows a man who has killed his wife to say, ‘I killed her but it’s not my fault because she was having an affair or she provoked me in some way, by nagging or whatever’.”

Ms Harman, who says she is “minding the shop” while the Prime Minister is on holiday, added: “There is no excuse for domestic violence, let alone taking a life. Whatever happens in a relationship does not justify resorting to violence. So men who kill their wives will no longer be able to claim, ‘It’s her fault, she provoked me’.”

The proposals – which have already taken more than four years to draw up – create a new partial defence of “fear of serious violence”. Men and women facing domestic violence could argue that they were forced to kill their tormentor.

On average about 30 women a year try to argue that they were provoked into killing their abusive partners, but lawyers and judges are straining the law to its limits as these crimes are usually the result of a “slow burn” rather than taking place in the heat of the moment.

A spokesman from the Ministry of Justice said that the changes would make clear that someone who discovers a partner was having an affair would not be entitled to argue they had been seriously wronged.

The “words and conduct” partial defence would not apply to sexual infidelity. “There are many situations where passions run high and where people feel a strong sense of having been wronged, especially within close personal relationships,” the document says. “But such situations, however devasting for the invididuals concerned, are essentially commonplace and people need to be able to deal with them without resort to violence.”

The reforms are based on a 2006 review of the homicide laws by the Law Commission, the Government’s law reform body, and are backed by groups ranging from the Association of Chief Police Officers to Justice for Women.

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