Nabjeet Singh appearing in the Wellington District Court on fraud charges on Thursday.

He was meant to be investigating benefit frauds for the Ministry of Social Development – but Nabjeet Singh was instead carrying out his own.

Singh, 48, of Upper Hutt, created four fake identities, including children, to get invalid benefits worth almost $360,000 over the course of 12 years.

Judge Peter Hobbs, in the Wellington District Court on Thursday, said Singh accessed ministry records to alter the phone numbers of his fictitious beneficiaries, and accessed its computer system to allow payments to be made to them.

GRANT MATTHEW/STUFF Singh, a former MSD benefit fraud investigator, created four fake identities to claim benefits of more than $350,000.

"Your offending cannot be categorised as anything less than serious fraud," he told Singh as he sentenced him to two years and nine months in jail after he had pleaded guilty to 51 counts of fraud, including 41 charges of using a document for pecuniary advantage.

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He said Singh's offending involved a significant degree of pre-medidtation.

Singh created addresses in the Hutt Valley, dates of birth, names and variations of names, IRD numbers, bank accounts, a post office box, false children and schools, and cellphones numbers.

Singh accessed MSD's computer systems to recommend, authenticate and grant numerous payments to the false identities.

He obtained approximately $358,866 worth of funds that he was not entitled to.

Singh began working at MSD in 1990 in various roles from customer service to helpline adviser and case manager. He began working in compliance in July 2003.

Between 2004 and 2011 he worked as a field officer and investigator, roles that involved investigating and prosecuting benefit fraud. He resigned in August 2011.

An anonymous tipoff led MSD to investigate his case. It uncovered the fraud and began inquiries with other government departments.

Immigration NZ confirmed that none of the four identities was recorded on its database, and none had ever applied for a visa to enter NZ.

Internal Affairs also confirmed that none of the identities had NZ citizenship.

The Ministry of Education confirmed none of the children connected to them were on its database, while Births, Deaths and Marriages had no records of them.

Schools where the children were supposed to be enrolled showed no sign of them.

The Crown recovered about $260,000 from the sale of a house.

Singh's lawyer Robert Lithgow, QC, argued for home detention instead of a prison sentence.

"He accepts as an employee this should not have happened."

Police said in a statement on Thursday evening that the sentence of two years and nine months reflected the seriousness of Singh's offending.

"Singh's corrupt and dishonest behaviour whilst employed in a position of trust within a government ministry is exceedingly disappointing," Detective Senior Sergeant Brent Murray, of the Central Asset Recovery Unit, said.

Police successfully sought a forfeiture of property to the value of $263,956, which comprised the proceeds of the sale of a dwelling and Bonus Bonds.

"The Criminal Proceeds Recovery Act is highly effective ... In this case Singh misappropriated significant funds from MSD over a 12-year period and these funds have now been recovered by police on behalf of the community," Murray said.

"The message is clear: if any persons attempt to profit from crime, they risk the loss of their assets."