Amateur bullfighters have been filmed slaughtering calves in Spain as they imitate professional matadors.

Graphic footage released by campaign group Torture Is Not Culture shows fans of the blood-sport who want a taste of the real thing given young males - often under a year old - to kill.

Standing in the shoes of the professionals, aficionados are seen spearing the calves with banderillas before ramming a sword called an estoca through their shoulder-blades, aiming for the heart.

Animal rights campaigners have captured footage in Madrid of a style of Spanish bullfighting called becerrada, which uses calves instead of fully-grown males

Becerrada is typically practised by trainee matadors or - as in this case - fans of the blood-sport who want to imitate matadors but don't want to face a bull

While fully-trained matadors are often able to make the kill in one fatal blow, the amateurs are seen struggling - often having to stab the calf multiple times.

Puntilleros are also brought in to stab the animals in the spine with a dagger in order to end their suffering.

Filmed in Alalpardo, Madrid, the footage also captures distressing noises the calves make as the slaughter unfolds.

Marta Esteban of Animal Guardians said that calves make such noises because they are trying to attract help from their herds, and that adult bulls are less likely to make the sound.

Calves were used, she said, because inexperienced bullfighters 'don't dare' square up to a fully-grown adult bull.

As in professional bullfighting, the calves are speared with bandrillas before the 'matadors' attempt to ram a sabre between their shoulder blades, aiming for their heart

While professional matadors are trained to make their kill in one clean blow, the amateurs often have to stab the calves multiple times, prolonging their agony

'Calves are used by bullfighting students and aficionados – fans of bullfighting who want to give it a try, such as in this case,' she said.

'Since they don't know how to bullfight "properly" they put the instruments of torture in improper places.

'Often they extract them and nail them again and again after unsuccessful attempts, causing a torment without equal to these small animals.'

Jose Enrique Zaldívar, who leads a group of veterinarians opposed to bullfighting, demanded that shows involving calves – known as becerradas – be banned.

'Due to their young age, the strength and ability of these calves to react is much lower, and their degree of stress and anguish is much more accentuated,' he said.

'The becerradas, without a doubt, constitute one of the most terrible manifestations of animal abuse in our country, and should be outlawed as soon as possible.'

Graphic video captured by animal campaigners shows the calves calling out in distress for their herd, a sound they say adult males seldom make

While the activists ultimately want all forms of bullfighting outlawed, they argue that this should start with becerrada because it is the most cruel

The calves used for becerrada are always under two years old and often younger than a year, when their horns have only begun to develop

While the free show was largely snubbed by the public, campaigners claim that there were still children among the audience of roughly 100 people.

They argue that this contravenes the UN Committee on the Rights of the Child, which last year recommended that children should not take part in the events as either bullfighters or spectators.

'We demand that the authorities take measures to prohibit the active or passive participation of children under 18 years of age in the becerradas,' said Marta.

'We can end these especially cruel shows, which many bullfighting fans do not even like,' said Carmen Ibarlucea, president of La Tortura No Es Cultura.

'We urge all those who reject these spectacles to help us finish them by entering the campaign page and participating in some of the ways we suggest.'

A petition to stop the shows can be signed here