Jailed former Heart of the City boss Alex Swney is teaching fellow inmates how to read and write.
Swney, 59, was jailed for five years and seven months in June 2015, after being found guilty of tax evasion and "sophisticated" offending spanning more than a decade.
The crimes involved more than $4 million.
It is understood he will be eligible for parole in May.
New Zealand Howard League for Penal Reform chief executive Mike Williams, a former Labour Party president, yesterday told the Herald on Sunday of Swney's work with fellow inmates via one of the organisation's peer-to-peer literacy programmes.
"We get prisoners who can read and write to teach the prisoners who can't read and write how to. And Alex is involved in that," Williams said.
"He came to see me - he had been convicted but not sentenced. And he got my number from a mutual friend and rang me and said that he was thoroughly remorseful, but he knew he'd have to serve some time, and what use could he make of his sentence."
At the time the league was in the early stages of developing the peer-to-peer literacy programme, which is common overseas.
Swney had told the league that a "flood" of prisoners wanted help with their parole forms. A recent graduation for the literacy programme featured prisoners who had been taught by Swney.
Williams said such learning would make a huge difference to the lives of those men, including when they were released.
"Of course, there is an element of self interest in [Swney's involvement]. That goes down well with the parole board."
Swney pleaded guilty to charges laid by the Inland Revenue and Serious Fraud Office for offending that Judge Grant Fraser said involved a "gross breach of trust".
Among the offences were 229 false invoices used to obtain $2,527,005 from the Heart of the City organisation between February 2004 and October 2014.
He also pleaded guilty to not paying taxes of $1,757,147.