School psychologists are calling for smacking to be banned outright because it harms children's mental health.
The Association of Educational Psychologists (AEP) has put forward a motion to the TUC Congress calling for the banning of corporal punishment "in all settings".
Hitting children to discipline is banned in schools, although parents and carers can legally smack children lightly in the home if it is "reasonable punishment".
Legislation aimed at completely banning the smacking of children is currently being considered by the Scottish Parliament, while the Welsh Government is also moving toward an outright ban.
In its motion, the AEP calls on the UK Government to "acknowledge that physical punishment can have negative long-term effects on a child's development", and is ineffective as a method of discipline.
It is also calling for the "reasonable punishment" defence to be removed from the Children Act 2004, which critics say goes against the United Nations Convention on the Rights of the Child.
The move comes after the Scottish Government and MSPs from across all political parties backed the introduction of a new Bill at Holyrood to completely outlaw smacking.
If passed, the legislation would remove the defence of "justifiable assault" in Scots law, which allows parents to use physical punishment to admonish a child.
A consultation on banning smacking outright concluded in Wales earlier this year, and found 81% of parents think it is never acceptable to smack a child.
Huw Irranca-Davies, the Welsh Government's children and social care minister, said: "As a government, we want to ensure every parent recognises that it's never acceptable to smack a child.
"This is why we intend to bring forward legislation to make it clear that physically punishing a child is no longer acceptable in Wales."