An office worker has been jailed for stealing $4.5 million from a major transport firm.

The New Zealand Herald reports an employee of logistics group Mainfreight stole millions in a seven-year defrauding scheme.

The Auckland District Court has sentenced Sushila Devi Mosese to four years and six months in jail after she pleaded guilty. The prosecution sought a sentence of six to seven years.

Ms Mosese worked as a credit controller in charge of chasing Mainfreight’s outstanding customer invoices.

She set up and took control of a bank account under the name of a Mainfreight subsidiary, diverting a string of payments into it from 2006 onward.

Nearly 500 cheques were deposited into the account she controlled, from which she withdrew up to $850,000 per year.

Prosecutors said there were "errant journal entries" made to cover up the diverted cheques from Mainfreight customers.

She even over-billed customers for fees Mainfreight then had to refund, and used her ill-gotten gains to prop up separate companies she was running.

The multi-million dollar fraud was discovered in 2013 when Mainfreight started looking into its customer payments.

Mosese had been working for the company for more than 20 years, but court reports say she had a prior conviction in Fiji for stealing from an employer.