Australia has spent $2 million to transfer and support five refugees resettled in Cambodia under a controversial scheme, three of whom have opted to return to the countries they initially fled.

The revelation came from Australian Immigration Minister Peter Dutton, who defended the outlay, saying the resettlement program, widely criticised by human rights advocates, had stemmed the flow of boats carrying asylum seekers towards Australia.

“The fact that we’ve had no drownings at sea, no successful boat arrivals, I think is a pretty significant outcome,” Dutton told Australian radio on Thursday.

Dutton spent last week defending the $55 million arrangement, signed in 2014, after an Iranian couple, among the first four people transferred to the Kingdom in June last year, became the second and third volunteers to return home. Only two of five remain.

Cambodia was pledged $A40 million in aid to take refugees held by Australia on the Pacific Island of Nauru. Another $A15 million was handed to the International Organization for Migration to handle resettlement services.