TORONTO -- Prosecutors are seeking a "substantially longer" sentence for the man at the heart of the Maple Leaf Gardens sex abuse scandal, saying the penalty he received does not reflect the severity of his crimes.

The Crown has filed a notice of appeal in the case of Gordon Stuckless, who was sentenced last month to 6.5 years in prison for sexually abusing 18 boys decades ago.

Stuckless, 67, was given credit of six months for time served under house arrest, which means he will spend six years behind bars.

The ruling angered many of his victims, who said they have suffered much longer as a result of his actions.

In the notice filed with the Ontario Court of Appeal, the Ministry of the Attorney General argues Justice Mara Greene "erred by misidentifying the appropriate range of sentence in cases involving the prolonged sexual abuse of multiple victims."

The sentence, the document alleges, is "disproportionate to the gravity of the offence and the degree of responsibility of the offender," and "clearly unreasonable and demonstrably unfit in the circumstances of this case."

The notice also says Greene "over-emphasized the mitigating factors in the case and gave insufficient weight to the many aggravating factors."

Stuckless pleaded guilty two years ago to 100 charges related to the sexual abuse of the 18 victims, now in their 40s and 50s.

He was also convicted of two additional charges of gross indecency linked to two of the victims.

The Crown had called for a 12-year sentence, saying Stuckless preyed on young boys for decades and has not shown genuine remorse for his actions.

Stuckless's lawyer had pushed for a five-year sentence, with two years of credit for time spent on house arrest and steps taken to prevent recidivism -- namely the fact that Stuckless has voluntarily undergone chemical castration for more than a decade.

In handing down the sentence, Greene said Stuckless abused his position as a teacher and hockey coach to groom his victims but found he has since taken responsibility for his actions and worked to keep himself from reoffending.

Greene said she considered the "general range" of sentences for this type of offence in determining Stuckless's fate, and had to take into account the outcome of his earlier conviction on a similar case.

Stuckless previously pleaded guilty in 1997 for sex assaults on 24 boys while he worked as an equipment manager at Toronto's Maple Leaf Gardens between 1969 and 1988.

He was sentenced to two years less a day in that case, but that was increased to six years on appeal, less a year for time served. He was paroled in 2001 after serving two-thirds of his sentence.

The case currently being challenged deals with abuse that took place between 1965 and 1985. Greene said at sentencing that it involves several aggravating factors -- including threats of violence and four incidents of digital penetration -- that were not present in the first case, and as such, "something slightly higher is required."

The Crown has the right to appeal a sentence but such appeals are "very limited because appeal courts will not usually interfere with the trial judge's decision on sentencing," the Ontario Ministry of the Attorney General says on its website.

"When asked to review the sentence, the appeal court will consider whether or not the sentence is fair. The appeal court will look at the nature of the crime, the impact of the crime on the victim, the background of the offender and the sentences imposed in similar cases."

Stuckless's lawyer, Ari Goldkind, said he has not seen the notice of appeal or discussed it with his client and therefore cannot comment.