A security expert supports the idea that the Government's spy agency help police with criminal inquiries.
The Government Communications Security Bureau has been faulted for staging 56 spying operations involving 88 New Zealand residents.
Prime Minister John Key says this might turn out to be illegal even though the agency believed it was acting lawfully.
Mr Key wants to clarify the law, saying the GCSB should be able to help local law enforcement agencies monitor local people.
Trevor Morley, a former police officer turned security consultant, says this could be useful for police - particularly in trans-national crime.
He cites the example of a man who killed his wife in Auckland, dumped his daughter in Melbourne and fled to the United States before eventually being caught.
Mr Morley says GCSB's mobile phone monitoring equipment could have helped to apprehend him quickly.
