A Hastings horticultural labour contractor's historic convictions for people trafficking and slavery could be challenged in the Supreme Court.

An application has been filed on behalf of Joseph Auga Matamata for leave to appeal the 23 convictions, which were imposed in the High Court in Napier last year after a trial lasting more than five weeks.

He was sentenced to 11 years' jail, the convictions and sentence being upheld by the Court of Appeal in a decision issued last month.

The Crown had also appealed, to the Court of Appeal, seeking a higher penalty, and it was ruled Matamata should serve a minimum non-parole period of five years in prison.

The Crown is understood to have been advised late last week of the new bid to New Zealand's highest court, and is expected to file a response before the Supreme Court will decide whether it will consider a second appeal.

In the first prosecution of its type in New Zealand, Matamata had been convicted of offences against 13 workers he had brought to New Zealand mainly from around his own village in Samoa over as much as 25 years, from 1994 to 2019.

Giving evidence at the trial they told of at time not being paid, confinement and beatings, instead of the hopes they had had for earning a living in New Zealand and helping support families in the islands.

The Supreme Court has been New Zealand's highest court since 2004, effectively taking a role previously that of the Judicial Committee of the Privy Council in London.

Last year it granted nine applications for leave to appeal in criminal cases, and declined 48.