The heinous moment a priest slaps a crying baby across the face during a baptism.

A distressing video that shows a priest slapping a crying baby boy on the face during a baptism is angering social media users.

In the 43-second YouTube clip, which is understood to have been filmed in France, a woman believed to be the mother holds the child as the priest speaks in French.

When the boy starts to cry, the priest taps him on the forehead. Then, in an attempt to soothe the baby, he wraps his hands around his head and neck and pulls him into his chest.

But this only upsets the squirming child even more, whose screams grow louder.

Then in an appalling act, the priest clasps his hands on either side of the crying baby’s face, his voice much sterner, and slaps him loudly across the cheek.

Some people couldn’t even watch the whole clip. Post continues after video.

The watching crowd gasps in horror. A man presumed to be the father eventually manages to wrench the boy away from the priest as he disconcertingly once again tries to hug him close with one hand covering his face.

Reddit users have translated what the priest was saying throughout the video.

“This is called a tantrum. I’m going to pour water on the forehead. And then we will embrace this little guy because he will have become a little Christian,” he says.

“Oh lala lala. I can scream louder than you. So, calm down. Calm down. (Slaps the child.) Calm down. You need to calm down!”

The priest then continues to repeat “calm down” until the father pries his son away and he is told to let go of the child.

People are heard protesting the priest’s actions and saying the boy is “scared”.

Parents were among the many social media users expressing their utter disgust in response to the video.

“As a father, this made me instantly rage. Props to the dad for keeping his cool,” one man wrote.

“I couldn’t finish watching that,” said another.

“It’s not often a video makes me feel physically ill. This video made me feel physically ill,” another commenter wrote.

It’s an unbelievable situation for any parent to find themselves in.

What would you do if someone slapped your child? Tell us in the comments below.