In the first three months of this financial year, the SFO spent a further $369,463, with nearly $100,000 of that paid to a private investigation firm, Omega Investigations.
The marked rise in payments to contractors and consultants was a result of significant investigations, including South Canterbury Finance, Hanover, Belgrave Finance, Dominion Finance, Capital + Merchant Finance and Rockforte Finance.
"The complex nature of these cases requires specialist skills which have, in part, been met from external providers," the SFO said.
"SFO is now decreasing its dependence on external providers by recruiting additional forensic accountants, investigators and lawyers," the agency said in a statement.
The extra resources also led to 84 per cent of inquiries being completed within 12 months and the average inquiry length of less than six months, according to the SFO.
Staff numbers are likely to increase from 40 to 50, as the SFO budget will be given an extra $7.5 million over the next three years.
The $1.3 million spent in the 2010/2011 financial year also came after SFO director Adam Feeley was appointed in late 2009 and restructured the agency, which led to four senior staff being made redundant.
"If that experience was to be lost, it would be very hard to replace those people who have had ... a unique experience fighting white-collar crime in New Zealand," one Queens Counsel said during the restructuring.
Three of the senior staff - Gib Beattie, Ian Varley and David Osborn - had nearly 50 years of SFO experience and have since started their own forensic investigation firm, Beattie Varley & Associates.
Another 11 staff have resigned since September 2009.
At the time of the restructuring, Mr Feeley told the Herald the need for change was endorsed by other law-enforcement agencies, regulators and the insolvency sector, as well as major legal and accounting firms.
Big crime, big costs
Consultants' and contractors' costs:
* 2007/08: $97,356
* 2008/09: $200,872
* 2009/10: $401,926
* 2010/11: $1,318,967
* July-October 2011: $369,463