Pakistan's National Assembly passed legislation Thursday closing a loophole that allowed people who killed in the name of ‘honour’ to go free, mandating life imprisonment even if the victim's relatives forgive the murder.

Honour killings ‘claim the lives of hundreds of victims every year’, the bill stated, adding that the legislation was ‘essential in order to prevent these crimes from being repeatedly committed’.

Rights groups and politicians have for years called for tougher laws to tackle perpetrators of violence against women in Pakistan and the move follows a slew of high-profile killings in the country.

The perpetrators of so-called honour killings -- in which the victim, normally a woman, is killed by a relative -- often walk free because they can seek forgiveness for the crime from another family member.

A 2005 amendment to the law pertaining to honour killings prevented men who kill female relatives pardoning themselves as an ‘heir’ of the victim.

But punishment was left to a judge's discretion when other relatives of the victim forgive the killer -- a loophole which critics say is exploited.

The amendments passed Thursday and published on the National Assembly website mandate judges to sentence someone who kills in the name of ‘honour’ to life imprisonment, even if they have been forgiven, said senior opposition lawmaker Farhatullah Babar.

The assembly also passed a bill boosting the punishments for some rape offences.

Rape conviction rates are close to zero percent, largely due to the law's reliance on circumstantial evidence and a lack of forensic testing.