Up to six detectives are giving up their police duties to work with the Serious Fraud Office.
One is already working with the SFO and others are expected to start in the next few months.
SFO chief executive Adam Feeley says they will help on big fraud cases for about a year.
He says the SFO is dealing with some significantly larger than usual cases at the moment, such as Hanover Finance, requiring more staff.
Mr Feeley says the move will save money and is better than employing permanent staff who may not be needed later, when the workload lessens.
He says it will also help build bridges between law enforcement agencies and is a good career opportunity for the police involved.
With about 10,000 sworn officers in the police force, Mr Feeley says the secondments will not have a big impact on police numbers.
Former executive critical of move
However, a former Serious Fraud Office executive, Gib Beattie, says the SFO should be hiring new highly skilled investigators instead of temporarily recruiting police officers to help ease a heavy workload.
He says police officers may be of help with some aspects of casework but most are not skilled enough in forensic accounting to make a real difference.