The beating of children by parents is illegal, the European Court ruled yesterday.
The landmark judgment is a victory for a 14-year-old British boy who cannot be named for legal reasons.
Yesterday he was awarded £10,000 damages and £20,000 legal costs for a caning carried out by his stepfather when he was nine.
The judges said corporal punishment - still permitted under United Kingdom law as "reasonable chastisement" - was a breach of a child's human rights.
The verdict from the European Court of Human Rights in Strasbourg means changes must be made in British legislation to give children the same protection against assault as adults.
The boy's stepfather was acquitted of assault causing actual bodily harm at a jury trial, after pleading his attack on the child was only "reasonable chastisement", as permitted by British law.
But the boy, backed by his natural father, took the case to the Strasbourg court to test the law against the European Convention of Human Rights, to which Britain is a signatory.
The Save The Children charity welcomed the ruling and said: "Every child has the right to a life free from violence."
A spokesman said: "Millions of children in some European countries are already protected by a ban on all physical punishment. In countries which banned physical punishment some time ago levels of violence against children are lower than in the UK, there are fewer prosecutions for violence against children and fewer children taken into care."
Yesterday the nine human rights judges ruled unanimously that such punishment meted out by parents to children violates the Convention's Article 3, which states: "No one shall be subjected to torture or to inhuman or degrading treatment or punishment." The same decision was reached last year by the Human Rights Commission, which advises the court, prompting the British government to agree that domestic law should be changed.
The judges heard that the boy had been beaten with a 3-ft garden cane and that some of the blows were inflicted directly on to bare skin.
Officials at the Human Rights Court emphasised that the judgment concerns only the individual case involved, but acknowledged that it signalled the effective end of all but the mildest of parental smacking of a child.
UK adults are already fully protected under current assault laws - only children remain legally subject to "reasonable" corporal punishment in the home.