The number of completed prosecutions for sickness benefit fraud has risen by more than 40% in the past financial year.
The total number of people charged for benefit fraud increased by 13% over the same period.
In the last financial year, the Ministry of Social Development investigated almost 16,000 beneficiaries for possible fraud.
Statistics obtained by Radio New Zealand show that 1001 such cases were prosecuted in the last year, with a 94% success rate. That's up on 883 completed prosecutions in the previous year.
The number of completed prosecutions for fraud relating to sickness related benefits rose from 100 in 2006/2007 to 142 in the last year.
However, successful prosecutions for fraud over unemployment benefits dropped slightly to 250 over the last year.
The ministry says there is no trend to the figures and the prosecution data relates to a very small percentage of overall benefit numbers.
At the end of June, 258,000 people were receiving main social security benefits.
The ministry says it's responsible for the administration of more than $12 billion worth of benefit and superannuation payments per year.
Meanwhile a beneficiaries advocacy group says too many unemployed people are being treated as criminals.
Paul Blair, from the Rotorua Unemployed and Beneficiaries' Union, says there should be a threshold to the allegations the Ministry of Social Development chooses to investigate.
He says beneficiaries are left looking like bludgers and parasites on people who pay taxes.
But the ministry says it takes its obligation to protect the integrity of the benefit system very seriously.