Thousands of Welsh parents would be criminalised if a smacking ban is passed, campaigners have warned.
The Welsh Government wants to remove the legal defence for parents who use corporal punishment to discipline children.
But campaigners said removing the reasonable chastisement defence would leave "ordinary parents facing jail".
The Welsh Government said it would make sure the law made "life better for parents and children".
It is due to consult on the plans in the next 12 months.
Now a group of parents, known as Be Reasonable Wales, have started a petition calling on the Welsh Government to scrap the plans.
Mother-of-one Lowri Turner said there was a difference between smacking and abuse and the move would paint ordinary parents as "no better than violent thugs and child abusers".
She said: "They're trying to make out that a gentle smack on the back of the legs from a loving mum is the same as beating up your kids.
"Does anyone seriously think that that sort of abuse is not already illegal?
"If the government can't tell the difference then they shouldn't be passing laws about it."
The move would mean if an allegation of hitting a child is made against an adult, it would remove a defence for those who might argue they had not realised they had hit the child so hard.
Andy James, chairman of Children are Unbeatable, a campaign group in favour of a smacking ban, accused the group of "scaremongering".
He said the law had been changed to give children the same protection against assault as adults in 52 countries and there was no evidence parents would be criminalised by the move.
"No-one has a right to hit another person, or to punish and control them," he told BBC Radio Wales.
"Children should have the same protection from the law that we enjoy as adults."
A poll of 1,000 people by ComRes on behalf of the campaign group shows 85% of Welsh adults were smacked as children and close to 70% agree that it is at times necessary to smack a naughty child.
Children's Commissioner Sally Holland said she was "disappointed and saddened" people would actively campaign for their "right to hit children".
She added: "Fewer parents than ever resort to smacking these days and I believe that in the next generation we will look back on the current outdated law and find it astounding that we had a legal defence for hitting those more vulnerable than us."
A previous attempt to ban the smacking of children failed in the assembly in March 2015 when AMs voted against removing the defence of reasonable chastisement from the Violence Against Women, Domestic Abuse and Sexual Violence Bill.
But the Welsh Labour Government is trying again, saying it has made a "firm commitment to seek cross-party support" in the assembly to end the defence.
A spokeswoman added: "We will work hard to ensure that our legislation makes life better for both parents and children."
The assembly does not yet have powers to make laws on parental discipline, but these will be devolved to Wales from Westminster under provisions in the Wales Act.
- Be Reasonable Wales describes itself as a campaign of parents and supportive groups, supported by the Family Education Trust and the Christian Institute
- Children are Unbeatable Cymru's says its list of supporters includes the NSPCC, Action for Children, the Methodist Church in Britain and Churches for Non Violence