To say that English parents are uniquely keen on hitting their kids wouldn’t be fair – even on a day when the Welsh government’s announcement that it aims to outlaw corporal punishment leaves England looking isolated. What can be said with confidence is that English parents, and the MPs who represent them, appear unusually determined to hold on to the legal right to “smack” their offspring.

I say “smack” because that is the term most often used, though whether these blows or slaps are really distinguishable from others is a moot point. Certainly most smacks aren’t issued as formal penalties, as used to happen in schools or households in which discipline was a matter of “Wait till your dad gets home”. Currently the UK is one of just two countries in the EU (the other is the Czech Republic) neither to have banned corporal punishment, nor to be considering a ban.

One survey by the NSPCC reported almost half of British parents of children aged between 11 and 17 as saying they had smacked them, but the lack of international research makes comparisons difficult. In one of the few surveys of families across Europe, 70% of French parents said they had slapped a child’s face, while just 8% claimed to be raising children without any violence.

It is widely agreed that corporal punishment is becoming less common in the UK, as it is in most places. But the idea that British parents should be allowed to change at our own pace, and not be threatened with sanctions, is tenacious.

The problem for politicians, when faced with the prospect of tabloid ire about a ban, is that the law matters. This is partly practical. Changing laws alters behaviour much more dramatically than any amount of nudging or peer pressure, though public education is important. But law is also a matter of principle. Bruce Adamson, the children’s commissioner for Scotland (where the government has thrown its weight behind a ban), is a lawyer who believes the human rights case for “equal protection” from violence can no longer be ignored with regard to children.

Just how strange it is that British children don’t currently have the same protection as adults takes a bit of thinking about. Take me, a mother with a fairly quick temper. I would never set out to smack my children because I don’t believe in it, but I’ve more than once grabbed or handled them roughly, and once slapped a leg when furious.

I’m not proud of this. In fact I’m sorry about it, and own up here only because it feels hypocritical not to. But my point is this: when it’s so obviously more wrong to swear at small children, or scream insults at them, than it is to do the same to your spouse or another adult, how can it not be worse to lash out physically as well? How can it be that a defence exists for an assault on a toddler (as long as it doesn’t leave a mark) that doesn’t exist for an assault on a grownup?

There are two main answers to this. One of these is that smacks aren’t assaults – they are punishments. The evidence, however, doesn’t support this. Joan Durrant, a professor of community health sciences at the University of Manitoba in Canada, says that decades of research point to the idea of the orderly smack – delivered to teach a child a lesson – being a fallacy.

Adults mostly hit their children when enraged and out of control, and language plays a key role in masking this. Just as the term once used to describe victims of domestic violence as “battered wives” had a useful (to abusers) double meaning, suggesting someone worn out rather than beaten up, so child-hitters have their own special word: “smack” is designed to dissociate thumping a child from other forms of violence.

The other justification often given is that even if hitting children is wrong, it’s even more wrong for police and courts to interfere in family life. The fear of spurious prosecutions, of good and loving parents being criminalised, looms large in arguments against change. Here New Zealand offers a reassuring lesson: in the three years after the banning of physical punishment, the government found that the dreaded “unnecessary state intervention” in private homes did not happen.

How can it be that a defence exists for an assault on a toddler that doesn’t exist for an assault on a grown-up?

Hardly anyone defends smacking per se any more. A growing body of evidence since the 1980s has shown it to be harmful rather than beneficial – as was once believed by many Christians influenced by such teachings as “spare the rod, spoil the child” – and to have links to violence of other sorts, including spousal abuse.

Such evidence is one reason why the Global Initiative to End All Corporal Punishment of Children exists, and also explains why countries including Canada have imposed age restrictions. There, smacking is only legal between the ages of two and 12. In the UK, there is no bar to parents (or any babysitter who has a parent’s permission) hitting babies or older children, while the government’s recently updated definition of domestic violence includes a paragraph on adolescent abusers, and another on male victims, but almost nothing about victims under 16.

Durrant believes the real reason why hitting children is still allowed is that they lack political representatives. The “reasonable punishment” defence, she points out, dates back to ancient Rome, when it was applied to slaves, along with women and children; and a key development in the common law was the 1860 trial of Thomas Hopley, a London schoolmaster who flogged a 15-year-old boy, Reginald Cancellor, to death, in an effort to “cure” bad behaviour. While Hopley was convicted of manslaughter, the judgment asserted that “reasonable” beating was allowed – an idea subsequently exported to British colonies worldwide.

For many children, occasional displays of temper by a parent, sometimes accompanied by a light slap or uncomfortably firm hold, are part of life. What is increasingly clear is that the strenuous efforts to deny any connection between what is sometimes called a “loving smack” (that is, an occasional blow from a good parent) and “abuse”, don’t stand up. Research on the mistreatment of children shows that in many cases the cycle begins with punishment.

There is no guarantee that a smacking ban would lead to a diminution in the kinds of child cruelty cases that make us flinch when we read about them. But it is worth noting that Sweden, the first country in the world to outlaw hitting children, has one of the lowest child abuse and homicide rates in the world.

Change takes time and people are resistant, as the Welsh government has acknowledged, not least because we feel protective of the methods used by our own parents. But with smacking either prohibited or on the way to being so in more than 100 countries worldwide, and the UN convention on the rights of the child clear in its commitment to “end violence” of all kinds, England has some catching up to do. Children’s commissioners in all four nations of the UK, along with the NSPCC and campaigns including End Violence Against Women, are convinced it’s a case of when, and not if. Now would be good.

• Susanna Rustin is a Guardian writer and editor