Animal welfare authorities are outraged after a horrific photo of a teenager holding a knife to a dog's throat emerged online. 

It's alleged the the photo was posted to Facebook by a teenager in Hervey Bay in Queensland.

It shows the boy grasping the animal's face with one hand and holding what appears to be a knife in the other. 

The RSPCA said they were horrified by the image and hoped it was a hoax. An RSPCA Inspector reportedly told Seven News it has investigated a formal complaint and the dog is well cared for and not in danger. 

A family member of the teenager has defended his actions, saying he was 'forced to do it' and the knife was a toy. 

Despite the omission the picture has angered many on social media who are calling for the teenager to be charged.