Perhaps it is unsurprising that senior staff seem set to walk away from the Serious Fraud Office when a restructuring is announced this month.

Their lot over the past few years has not been an entirely happy one.

One or two losses in high-profile cases have sparked a level of criticism that failed to acknowledge a generally solid record in tackling white-collar crime.

Helen Clark's Government threatened to abolish the SFO and merge its functions with a police unit.

Having survived that, the SFO is now facing a renewed barrage of criticism and an overhaul that seems likely to comprehensively change its mode of operation.

Judith Collins, the Minister Responsible for the SFO, has talked of rebuilding "its capabilities after years of political neglect".

Addressing the Trans-Tasman Business Circle in February, she spoke of the role the SFO would play "in strengthening enforcement of business regulations and maintaining New Zealand's reputation as a clean, corruption-free and safe place to do business".

The minister went as far as to suggest that one of the key challenges for the SFO's new chief executive, Adam Feeley, would be "to detect and catch crime before it happens, rather than long after investors' money has dissipated and cannot be recovered".

This implies that the SFO should accept much of the blame for the losses suffered in the collapse of finance companies. That is unfair.

The challenge Ms Collins put to Mr Feeley is one that should be met by regulatory agencies, such as the Securities Commission.

The SFO's brief is to investigate and prosecute serious cases which are defined as fraud involving more than $500,000, fraud perpetrated by complex means, or fraud likely to be of public interest.

As such, it sits at the bottom of the cliff. Recently, that role has involved deciding whether charges would be laid in cases involving finance companies such as Bridgecorp and Blue Chip.

Mr Feeley, formerly the chief executive of the Eden Park Redevelopment Board, has delivered his own criticism. "I think the SFO could have moved faster," he said.

In some instances, he may be correct, but any criticism should recognise that fraud is the most difficult of crimes to detect. It is even more difficult to prove its intent beyond reasonable doubt.

Often, it is complex, sophisticated and difficult to untangle. It is reasonable to ask whether more of the SFO's cases would have come unstuck if, in haste, it had paid less attention to detail.

Mr Feeley's draft restructuring plan includes effectively outsourcing some of its role.

Meredith Connell, the law firm that holds the Crown warrant for prosecutions, and accountancy firm PricewaterhouseCoopers would be closely involved with future SFO investigations.

The cost-effectiveness of such an approach is open to question. Equally, it hardly represents a ringing endorsement of the current SFO personnel.

The upshot appears to be that five senior staff with more than 70 years of fraud investigation experience among them, including Gib Beattie, the present assistant director, are unlikely to reapply for new roles.

All have been involved in high-profile cases, including, most recently, that of ASB Bank fraudster Stephen Versalko. If they depart, the SFO will lose a huge fund of institutional knowledge.

It will surely face a greater struggle to combine with other regulators to ensure the "speedier, united response to cases of suspected fraud" demanded by Ms Collins.

Too much of the criticism of the SFO has been over the top. It should not be the whipping boy for the finance-company debacle and nor should it be restructured in such a way that valuable experience is driven away.

If a wiser approach is not adopted, white-collar criminals will be the only winners.