The Serious Fraud Office's power to compel suspects to answer questions will be removed when it is merged with the police organised crime unit.
The Government will today unveil details of its new-look Organised and Financial Crime Agency, designed to get tough on gangs and white collar criminals.
The agency will be run by the police, who will absorb the SFO's 33 staff and merge them with their own organised crime team.
But the agency will not retain all of the SFO's powers.
Suspects will able to refuse to answer questions, a right not available to them when they faced Fraud Office questioning.
The new agency will also have to convince a judge to order suspects to hand over documents.
The SFO was able to demand to see documents, regardless of defences such as client confidentiality.
But the new agency will have a broader scope than the SFO, ranging from gangs to international crime rings.
It is expected it will seek documents from gangs, which police claim are running increasingly sophisticated criminal enterprises.
The reduction in powers will bring the new agency into line with rights given to everyone under the Bill of Rights - a law which did not exist when the Serious Fraud Office was set up 21 years ago to fight white-collar crime.
But with the election months away and law and order certain to be a major issue, anything which appears to be weakening the powers of law enforcement will give ammunition to parties calling for a tougher stance on crime.
The main concern voiced last September when then-Police Minister Annette King revealed that the SFO was to be disestablished was whether the new agency would be given the same powers.
SFO assistant director Gus Andree Wiltens said that if white collar crime was to be tackled seriously, the new agency had to retain the fraud office's current powers, "and nothing less".
In his final annual report, made in October, retiring SFO head David Bradshaw said serious and complex fraud remained an issue, but that every year, several cases his office investigated would not be regarded a priority by police.
Mr Bradshaw also questioned whether the balance of New Zealand's laws was tipping too far in favour of the rights of defendants.
The Government is expected to counter accusations of being weak on crime by highlighting the new agency's position as the core component in its Organised Crime Strategy - also to be released today.
The strategy will promote community safety, intelligence gathering and law enforcement as part of a wide-ranging attack on organised crime.
A TVNZ Colmar Brunton poll this week showed 80 per cent of those questioned supported making criminal gangs illegal.
The Government wants to push through the merger of the Auckland-based SFO and the Wellington-based agency as soon as possible.
The Herald revealed last month that several specialist staff had left the SFO, and the Government wanted to retain remaining SFO staff.
Jeremy Bioletti, an SFO prosecutor from 1990 to 1994, told the Herald at the time that the Government was deluded to axe the SFO because corporate fraud remained such a serious issue.
"Many of the SFO people are professional accountants and lawyers. Why would they want to join an organisation run by the police?
"Without their brains and ability the police will simply not be up to the task."
* THE CHANGES
Serious Fraud Office
Can make people answer questions or supply information, overriding the right to silence.
Can require people and companies to hand over documents and information, regardless of client confidentiality.
Organised and Financial Crime Agency
Will not be able to override people's right to silence.
Will need a judge's permission to make people and companies surrender documents.