Most parents believe smacking is an acceptable way to discipline children, according to a survey.
The figure was higher among adults without their own families, 80% of whom said they would support smacking as a punishment if necessary.
But, among parents, the proportion who smacked their children fell to 67%, the poll for ITV showed.
The survey was conducted ahead of a new ITV1 documentary, I Smack And I'm Proud, which follows five families who smack to discipline their children.
Parents aged 35-54 were most likely to have smacked their children, with nearly three-quarters - 74% - saying they had done so.
The vast majority of adults surveyed said they would oppose any moves to introduce an outright ban on smacking.
The poll found that between 80% and 90% of both parents and adults without families were against a complete ban. Similar proportions said they did not consider a light smack as the same thing as hitting a child, despite the concerns of children's charities.
Many adults were concerned about violence and unruly behaviour among teenagers in public and were worried that a ban on smacking would erode discipline further.
The survey also suggested widespread ignorance about current laws on smacking. Only 43% understood the law in England and Wales, which states that mild smacking is legal but any blow which leaves a mark on a child is illegal and could result in action, the ITV study said.
GFK NOP media surveyed 1,939 adults in the UK for the survey last month.
