A former Corrections employee who tried to persuade a teenager not to give evidence against a man who abused her has not had her sentence changed on appeal, despite a ruling the judge got it wrong "by a wide margin".

Helen Diana Potter was sentenced to 10 months home detention last year after being found guilty at trial of attempting to pervert the course of justice.

The Solicitor General challenged that decision and in a decision released today, the Court of Appeal accepted the sentence was "manifestly inadequate and inappropriate".

The appeal judges said a jail term of two years nine months would have been the correct penalty but imposition of that penalty was impossible due to a legal technicality.

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In August 2012, Helen Diana Potter heard about accusations made by a teenage girl against her 48-year-old partner Mana Tamaiparea.

A month later, the complainant had made a formal written statement for police withdrawing the allegations but when she changed her mind again Tamaiparea finally went to trial in March 2014.

The jury heard about Potter's influence when the young victim gave evidence.

She had pressured the girl before and during the car ride to the police station to give a statement.

"On both occasions, the pressure had taken the form of Ms Potter telling her about the financial consequences of Mr Tamaiparea going to prison, in particular because he was helping to pay the rent and to pay for the things the complainant needed both at home and at school," the judgement said.

The jury could not reach a verdict against Tamaiparea but he eventually pleaded guilty to a representative charge of indecent assault in October.

He was sentenced to a term of preventive detention at the High Court in Christchurch earlier this month.

In sentencing Potter, Judge Paul Kellar gave her a discount for her previous good character and her work as for Corrections 15 years earlier, which he said would make a prison term more difficult for her to serve; eventually settling on a term of home detention.

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The Court of Appeal said the starting point adopted by Judge Kellar was "inadequate by a wide margin" and his reduction for the defendant's previous career was wrong.

However, Potter's sentence remained unaffected and she will finish her period of home detention in June.