People who still used hot irons to brand livestock should face criminal charges, the National Council of the Society for the Prevention of Cruelty to Animals (NSPCA) said on Friday.

"Forcing smouldering pieces of metal into the faces of baby animals is tantamount to torture," the NSPCA organisation said in a statement. The practice is not illegal.

"We believe the time has come to lay criminal charges and to pursue the matter vigorously through every legal channel available to us."

The NSPCA has footage, taken by an inspector, showing calves as young as six months being iron-branded.

"The reaction of the young animals is clear as they bellow and recoil in pain," it said, calling this "unacceptable".

The organisation questioned the mindset of the people who watched the procedure and those who performed it on animals' faces.

"They are just small, helpless and trusting animals," it said.

The justification from within the farming industry was that branding is a legal requirement.

The NSPCA acknowledged that some means of identifying livestock was needed because of stock theft, but recommended freeze-branding or branding animals' rumps or hind-quarters.

"Hot branding is bad enough and the we vehemently oppose this method... the matter is being forcefully pursued and... a docket against the perpetrators is in preparation," it said.