Fabian Meharry, 28, asked 22 girls he met on social media websites to send him sexual photos of themselves, then used these to blackmail them to perform degrading and painful sexual acts, in one case over a number of years.

The girls were aged between 11 to 17 years.

In March, County Court Judge Liz Gaynor sentenced Meharry to 12 years' prison with a 10-year non-parole period 

Director of Public Prosecutions, John Champion, SC, launched an appeal to the decision in the Court of Appeal on Thursday.

The Office of Public Prosecutions said in a statement that prosecutors would argue that "the individual sentences, the total effective sentence and non-parole period were manifestly inadequate".

Judge Gaynor previously described Meharry as a "monster of depravity", saying he deliberately targeted young girls because they could be exploited to do what he wanted.

When his victims refused to perform sexual acts according to his instructions via webcam or Skype, he would threaten to publish the photos online or to send them directly to their families.

Meharry pleaded guilty to more than 60 child sexual abuse crimes including producing child pornography, sexual penetration of a child under 16 and grooming children using a carriage service. 

The court heard Meharry told his victims about his internet business, which sold wax for bikes and skateboards as a way to attract them to him, the court heard.

"It was as if you saw the internet as providing you with a vast array of vulnerable teenagers whom you could prey upon, exploit and terrorise, as the whim took you," Judge Gaynor said.