WARNING, GRAPHIC VIDEO: THIS is the sickening footage of a savage attack on a defenceless baby kangaroo that will anger the nation.

Wildlife activists wept in court this week as the chilling footage was made public for the first time in a push for tougher sentences for animal cruelty offenders.

Throughout the 35-second film three men can be seen tormenting and torturing the frightened kangaroo, laughing as they slap it, kick it in the head and throw it around.

In August Brett Saunders and Zachary Hunter were fined $800 and placed on good behaviour bonds after pleading guilty to their part in the attack.

WARNING: The below video contains graphic images

Scott Saunders, the brother of Brett, also pleaded guilty to his involvement and was fined $2500 and placed on a good behaviour bond.

During the film, that was shot by one of the attackers on a mobile phone, Scott Saunders is seen repeatedly hitting the frightened animal with a stick before slapping it numerous times in the head.

In documents tendered to the court one witness recalled the kangaroo looked like it "had been so traumatised it just stood there in terror".

Shortly after the initial attack Hunter can be seen in the video running up to the already injured joey and kicking it in the head, sending it airborne.

Animal rights activists Vicki Lloyd-Smith and Jane Heald made their feelings known when Brett Saunders left the Seymour Magistrates' Court in August. Picture: Stuart Walmsley Source: Herald Sun

The limp baby roo is then picked up by the tail and thrown several metres before it slams into a tree trunk.

Throughout the film the three men can be heard laughing before saying they planned to drop the dead kangaroo in the middle of a street.

The joey had been caught by a dog and put into the boot of a car that the Saunders brothers were travelling in.

It was later taken to Lions Park in Seymour where it was brutally killed.

Zachary Hunter, 23, pleaded guilty over his role in the incident that led to the joey's death in October last year. Picture: Stuart Walmsley Source: Herald Sun

Brett Saunders played no role in the actual attack on the animal other than to catch the joey.

The incident sparked widespread outrage with some animal rights' activists calling for the men to be jailed.

The footage was shown by Victoria's Director of Public Prosecutions John Champion, SC, who has launched a County Court appeal against the non-conviction sentences of the men.

The landmark appeal is believed to be the first of its kind where the victim of crime is wildlife.

SHOCKING: One witness recalled the kangaroo looked like it "had been so traumatised it just stood there in terror". Picture: SUPPLIED

It comes as wildlife experts say there has been a worrying spike in wildlife assaults across Victoria over the past year.

Lawyers for the men this week said they had suffered harrassment and received death threats since the incident was made public.

But DPP John Champion, SC, argued the men's sentences were "manifestly inadequate" and said tougher punishment was in the public interest.

Australian Society for Kangaroos spokeswoman Fiona Corke said she hoped the appeal would deter future perpetrators of animal cruelty crimes.

shannon.deery@news.com.au