National is calling on Justice Minister Kiri Allan to launch an inquiry into the Crown's handling of the Jayden Meyer rape case and its implications.

The call comes days after the Crown failed in its bid to throw out Meyer's home detention sentence and replace it with prison time.

"The Crown failed this week in its appeal of the sentence of nine months home detention, following Meyer's conviction on four counts of rape," National's justice spokesman Paul Goldsmith said in a statement today.

"Most New Zealanders are incensed by what the High Court called a 'manifestly inadequate' sentence for such serious crimes and the message it sends to victims of such crimes."

Goldsmith said the inquiry should consider a number of factors including why the Crown missed the deadline for appeal, and why a term of imprisonment was not initially sought by the Crown.

It should also consider whether the sentencing regime gives too much scope for judges to reduce sentences, he said.

"It's fair to ask if a system that allows a judge to take what was generally agreed to be a crime that warranted an eight-year prison sentence down to nine months home detention is fundamentally too loose.

"Confidence in the justice system is one of the most precious things in our democracy. The Minister should move swiftly to reassure New Zealanders following this outcome."

The home detention sentence sparked protests. Photo / Andrew Warner

• Jayden Meyer's home detention sentence is appealed by Crown
• The Crown's appeal in the sentencing of teen rapist Jayden Meyer has been dismissed

Open Justice revealed last month how the Tauranga teenager was sentenced to nine months' home detention for the rape of four 15-year-old girls and the sexual violation of another. He was 16 at the time of the offending.

The sentence drew the ire of the public, sparking numerous public protests.

Originally, both Crown prosecutor Anna Pollett and Meyer's lawyer Rachael Adams submitted that a sentence of home detention would be most appropriate - despite Pollett accepting imprisonment would be the ordinary sentence for this sort of offending; "and indeed one of many years".

Then last week Deputy Solicitor General Madeleine Laracy sought leave to appeal the sentence of home detention in favour of prison time, six weeks outside of the statutory window for appeal.

High Court Justice Sally Fitzgerald, who considered the application, released her decision on Wednesday, declining the bid for an appeal.

She said with Meyer now attending a sexual violence rehabilitation programme, the logistics of managing this within prison would be difficult.

"Given the delay, Mr Meyer has served over a third of his sentence.

"I accordingly accept that to sentence Mr Meyer now to a sentence of imprisonment carries with it a real risk of undermining progress to date in rehabilitation, through his engagement in an appropriate youth sexual offending programme. This is a particularly important factor in my view."

While dismissing the application, Justice Fitzgerald gave a scathing review of how the case was handled.

She said it was an error of law for the sentencing to proceed as it did, describing the process as lacking transparency.

"Whether the end sentence is around three years' imprisonment as suggested by the Crown or somewhat higher for the reasons just given, the Judge's sentence of home detention was manifestly inadequate. The fact the Judge did not engage in an orthodox sentencing analysis obscures the reality of this conclusion.

"Given the approach adopted by the Judge (which to be fair to him, was supported by the Crown), the sentencing exercise lacked transparency, which in turn undermines public confidence in the administration of justice."

- by Tara Shaskey, Open Justice