The Lords is to vote on an amendment to the Children's Bill allowing "moderate smacking".
BBC News Online talked to two charity officers who hold opposite views on smacking.
Iain Bainbridge, Christian Institute development officer
Discipline is part of love.
The current law only allows moderate and reasonable chastisement, therefore parents who use unreasonable or immoderate physical punishment can already - and should be - prosecuted.
Also, other sanctions that parents may use instead of smacking, like resorting to sarcasm or withdrawal of affection, can be more damaging.
The other argument that people use is that smacking is violent, and violence is wrong.
But of course there are many circumstances where some kind of physical impact is permitted and seen as acceptable.
For example, if a surgeon operates on somebody, the motivation is to help the patient, and again, with physical punishment the parents' motivation is to discipline and train a child.
Another argument is that in the last couple of decades we have outlawed physical punishment in schools. And what have we seen? More civility, less bullying?
No, we've seen exactly the opposite. And now an increasing number of teachers are leaving the profession because of the total lack of discipline, and even teachers being assaulted.
So we would say that it's wrong to criminalise loving parents for using moderate physical punishment. What moderate means, is for the courts to decide in the coming law. We think that's the best case.
With regard to what is being proposed, I have seen that there is an amendment being put down to the children's bill - it's extremely restrictive.
The vast majority of parents use their own common sense, but the way to go forward is not to further restrict the freedom of parents and to plunge the vast majority of them into legal confusion and the possibility of prosecution for using reasonable and loving discipline.
The ironic thing about all this is that the government's own Office of National Statistics survey found that 89% of people think it's sometimes necessary to smack a child.
Groups like the NSPCC, who are part of the Children are Unbeatable campaign, are actually seeking to criminalise their own supporters because the vast majority will at least at some point in the past have used physical discipline on children.
Finally, if smacking is made criminal, that means social workers and police will have to investigate all sorts of trivial cases, and that will prevent them from being able to concentrate on cases where children are actually physically abused.
Lucy Thorpe, NSPCC policy advisor
What we are actually talking about here is children having the same protection as adults under the law on assault.
That would send a clear message to parents and everybody else that hitting children is as unacceptable as hitting anybody else in the society.
What we have at the moment is a situation where children actually have less protection under the law on assault rather than the same as adults.
The poll that Children are Unbeatable have released shows seven in 10 people would want a change in the law to give children adequate protection.
We do know from our own research that attitudes are shifting. A majority of people believe that it's wrong to hit babies and toddlers.
The fact remains that there is a Department of Health research that shows many babies have been hit by the time they are one.
The difficulty is, we have a law that dates back to 1860 which is failing to protect children.
On the one hand we have professionals who are trying to protect children and send out messages in terms of positive and non-violent parenting, and on the other we have a law that says that children can be hit by their parents.
This is clearly an anomaly and it hampers effective child protection and family support.
We at the NSPCC don't just want a change in the law - we want much more widespread support and education for parents on the benefits of positive non-violent discipline.
I know that the discussion is often based on 'what harm does a light smack do'.
It may do no physical harm, but there are several things attached: we know that physical punishment can in some cases escalate and turn into abuse.
Also, it sends a clear message to children: that might is right, that if you don't like what someone is doing to you should resort to physical force.
Now, in terms of domestic violence between adults we would not accept for a wife or husband to give their partner a tap or smack, and it should be the same for children.
In terms of promoting good family relationships we don't want undisciplined children more than anybody else does, but we do want children to be brought up in a loving and supporting household where positive, non-violent discipline is used, which actually helps children learn about their behaviour and develop self-discipline.
If you rely on physical punishment you are teaching a child to be afraid of you, and you are potentially storing up a lot of problems: children can feel hurt, angry and resentful.