"The film that we are showing is particularly shocking now that Christmas is upon us, but it clearly shows the cruel reality that reindeer are exposed to," Roger Pettersson, secretary general of WSPA Sweden, said in a statement on Monday.
The footage also shows a reindeer being killed by a knife stab to the neck, as well as animals being earmarked by knife without anesthesia.
"This must be stopped immediately," Pettersson told news agency TT on Monday.
WSPA tasked a journalist with investigating the conditions for reindeer on their way to slaughter.
"He followed the reindeer herding and observed the gathering, selection, transport and slaughter, and evidence shows a high stress level for the animals. The reindeer are stressed during transport and their antlers become entangled. Even during branding, the animals are treated poorly," said Pettersson.
He said it is a challenge to handle reindeer, which are semi-domesticated animals and not accustomed to people.
"Densely packed into transport vehicles, reindeer antlers become weapons. They get caught in the sides of transport vehicles and they can even hurt each other before they reach the slaughterhouse," Pettersson said in a statement.
As such, Pettersson advocated the use of smaller mobile slaughterhouses such that the slaughterhouse move, not the reindeer.
According to the WSPA, the problem of distressed reindeer is similar in all Nordic countries. It said it will call on the the Nordic Council of Ministers to urge it to act.
The council adopted a declaration in 2008 that animals should be treated as sentient beings, have intrinsic value, and should be respected accordingly.
However, the Swedish National Sami Association (Svenska Samernas Riksförbund, SSR) has rejected the WSPA's claims that reindeer are subjected to cruel conditions and vowed to take action against herders who use unsanctioned methods.
"From the reindeer's point of view, we do not accept slaughter methods that are not sanctioned by the authorities. We take a stand against individual reindeer owners who use knives in organised slaughter," Jorgen Jönsson, the chairman of the SSR, said in a statement on Monday.
SSR national director Anders Blom added that he is adamantly against the use of a knife to kill reindeer.
"This is naturally something that is upsetting, but we have nothing against someone observing how we do our job. We have nothing to be nervous about," SSR national director Anders Blom told TT on Monday.
"We only use approved methods and have been working with government agencies to create programs for the treatment of animals based upon existing regulations," he added.
Research by the SSR, in collaboration with Sweden's University of Agriculture (Sveriges lantbruksuniversitet, SLU), shows that the stress levels of reindeer which are slaughtered has decreased during the last couple of years and are now at acceptable levels, according to Blom.
"You measure the animals' pH levels. The limit for a healthy animal that is not stressed during slaughter is 5.8. Fifteen years ago, 30 percent of the animals were above that value – today it is 8 percent. Most show no signs of stress," he said.