Smacking children does not improve their behaviour and may actually increase behavioural difficulties, a new study has claimed.
Researchers from University College London (UCL) analysed 20 years of research on physical punishment by looking at 69 global studies.
They followed children over time and assessed data on smacking, finding that approximately 250 million children around the world are subject to physical punishment.
The study came to the conclusion that smacking does not improve behaviour and can in fact make things worse.
Lead author Dr Anja Heilmann, from UCL's Department of Epidemiology, said: "Physical punishment is ineffective and harmful, and has no benefits for children and their families. This could not be clearer from the evidence we present.
"We see a definitive link between physical punishment and behavioural problems such as aggression and antisocial behaviour.
"Even more worrying are findings that children who are the recipients of physical punishment are at increased risk of being subjected to more severe levels of violence."
The findings, published in medical journal The Lancet on Monday, suggest the link between physical punishment and increased behaviour problems is causal.
However, there were no signs that smacking resulted in a reduction in bad behaviour.
The study added that smacking also showed no improvement in children's attention, cognitive abilities or social competence.
Only 62 countries in the world, including Scotland and Wales, have banned smacking and England is one of four European countries where parents can legally use physical punishment if it is "reasonable".
But if the physical punishment leaves a mark, such as a scratch or a bruise, parents can be prosecuted for assault.
Scotland banned the practice in November 2020 before Wales followed suit
The study authors have now called for the practice to be made illegal in England, Northern Ireland and all the remaining nations.
Former Senator in the Irish Parliament and co-author of the paper, Jillian van Turnhout, said: "This review has documented compelling evidence that hitting children doesn't work, and in many cases, it is harmful.
"A home should be a safe place for children, yet in many countries, the law can make it one of the most unsafe places for them.
"Countries need to do all they can to ensure that all children have equal protection from all forms of harm, including physical punishment."
Joanna Barrett, from the NSPCC, added: "This is yet another significant study that shows physical punishment is harmful to children.
"It cannot be right that in 2021 children are the only group in society that it is legally acceptable to assault in England. The case for reform is beyond doubt."
But the Be Reasonable campaign, which opposes smacking bans, said: "Parents who love their children should be trusted to decide when a smack on the bum is appropriate. Ordinary mums and dads are fed-up of so-called experts demonising their parenting.
"Scientists can tell us many things but they cannot tell us whether smacking should be a criminal offence."