Australian parenting expert and a father of six Dr Justin Coulson said while parents might want to persist, forcing an upset child to sit on a stranger's knee is never okay.
'If a child is distressed or non-consenting then it's disrespectful and it can even be bullying to force a child to sit on a stranger's lap for a photograph,' Dr Coulson says.
'Parents who consistently disregard their children's fears, anxieties and feelings rob their children of agency.
'They increase the likelihood that their child will feel as if he or she doesn't matter or belong and they run the risk that this type of consistent behaviour will lead to genuine long-term psychological challenges.'
While Dr Coulson said there's no problem if a child is comfortable with sitting on Santa's lap for a photo, those who weren't needed their boundaries respected.
'We make a big deal about teaching children about body boundaries and about body safety and about consent,' he said.