Church leaders have called for smacking children to be completely outlawed in the UK, saying there are no circumstances where the "painful and humiliating practice" is justified.
The Archbishop of Wales Dr Barry Morgan is one of the leaders who has signed a joint statement with other prominent Christians, calling for the removal of the “reasonable chastisement” defence for parents who smack their children when they misbehave.
Views have long been divided on the benefits of physically punishing children. The law was tightened under labour in 2004, with parents banned from using force that causes "reddening of the skin".
But attempts to bring about an all-out ban have repeatedly failed.
A demonstration outside Downing Street against smacking, in 2004
A study published in October 2012 found patients who had cancer were 70% more likely to have been beaten as a child compared to the healthy group, researchers from Plymouth University found, something the NHS called "improbable".
But Labour MP, David Lammy, said in the aftermath of the London riots that parents should not be afraid to discipline and smack their children.
Dr Morgan wil use a speech at a vigil to mark Universal Children's Day on Tuesday to call for a ban on smacking.
He is expected to say: "Jesus believed that children were not just an asset for the future or a commitment to be undertaken for the sake of society. They were of infinite value as children.
"They deserved as much respect and care as any other human being.
"How can we ever think that smacking or using physical force on children can ever be right? None of us would ever dream of smacking an adult, why should we think smacking a child is any more acceptable?
"They too are made in God’s image, valued as the individuals they are. That does not mean that anything goes as far as bringing up children is concerned – but it does rule out physical punishment."
Archbishop of Wales Dr Barry Morgan, who has called for a ban on smacking
A joint statement issued with other senior Welsh Christians also condemned the practice: "Physical punishment of children has for too long been a common part of our culture.
"But physical punishment as a form of discipline is incompatible with the core religious values of respect for children’s human dignity, justice and non-violence.
"There are no circumstances under which this painful and humiliating practice can be justified."
Christianity Today reported that at the vigil on Tuesday, church leaders will light candles in prayer on behalf of children who have suffered violence, and Dr Morgan will wash children's feet.
The service is being supported by the charities Children in Wales and Children Are Unbeatable! Cymru.