Ministry of Social Development head of fraud Mike Smith said every client, including Ms McGreal, has a responsibility to tell the ministry of personal circumstances that might impact on their benefit.
"McGreal's actions were selfish. She made a decision to steal from taxpayers, but we caught her and ensured she was held to account."
He said the vast majority of clients are honest and receive their correct entitlement, but the ministry works hard to protect the integrity of the system.
The ministry established an intelligence unit in 2007 to identify emerging fraud risks and trends and has data matching programmes with six agencies including Housing New Zealand, IRD and Department of Corrections.
Mr Smith said the Masterton figures were not reflective of national trends - the number of prosecutions nationally dropped 12 per cent between 2009/10 and 2010/11, but the dollar value of the debt increased 42 per cent to $22.6 million.
He said the ministry received more than 11,500 calls to its Allegation Line in 2010/2011, and every allegation is followed up and investigated.
Roll of shame
Carterton woman Michelle McGreal was sentenced to six months home detention and 200 hours community work after being convicted on fraud and dishonesty charges in June 2010. She was overpaid by $77,800 after not informing Work and Income that she was living with her de facto partner.
In February 2011, Masterton couple Dalkeith Te Heke Matiaha and Fiona Margaret Wilton were convicted of five counts each of using a document to defraud. The pair both claimed the solo parents' benefit from 2005 to 2009, while living together. During that time, Wilton was overpaid by $56,000 and Matiaha by $53,000. The couple were sentenced to community detention and home detention, and ordered to pay back the debt.
In May 2011, Masterton woman Jean Love was sentenced to three months jail for fraudulently claiming $51,000 for an invalid's benefit. She did not report that she owned two houses as the beneficiary of a trust, while collecting a benefit between 2003 and 2010.