FREDERICTON -- The Crown in New Brunswick is seeking to appeal the sentence handed to a former city councillor in Saint John, N.B., convicted of sexually abusing and making pornographic images of boys, saying the trial judge gave Donnie Snook too much credit for time served in pre-trial custody.

Snook was sentenced in September to 18 years in prison after pleading guilty to 46 charges including sexual assault and possessing, distributing and making child pornography over a 12-year period. He was given 1 1/2 credit for time served, reducing his prison term to 16 years and 10 months, and he would be eligible for parole after serving one-third of that.

Crown prosecutor Karen Lee Lamrock is seeking to appeal, saying provincial court Judge Alfred Brien failed to consider a section of the Criminal Code that allows the court to limit credit for time served to one day for each day spent in custody to express society's denunciation for such offences.

In her application with the province's Court of Appeal, Lamrock also says the judge failed to consider a Criminal Code section that would require an offender to serve half their sentence or 10 years, whichever is less, before becoming eligible for parole.

Snook has also filed an appeal, saying the sentence was unreasonable and in excess of the appropriate range.

The Crown had argued at trial for a 21-year prison sentence, saying Snook created a "permissive atmosphere" in his home by luring boys with cash, allowing them to consume alcohol and marijuana, and having them carry out sex acts.

The crimes involved 17 boys between the ages of five and 15 at the time of the offences.

Snook was arrested by the RCMP after an investigation that began in 2011 involving the Saint John and Toronto police. After his arrest, police seized his computers and discovered more than 15,000 photos and videos of child pornography, the court heard.

Initially following the sentencing, Lamrock said she was satisfied with the judge's ruling, saying it was one of the longest sentences ever imposed in Canada for such crimes.

Snook still faces sentencing on four more charges from a separate case in western Newfoundland.

He is due in court in Saint John on Tuesday for sentencing on two counts of sexual assault and two counts of sexual interference.

Snook pleaded guilty to those charges last month.