This comes after a report from the New Zealand Aid Development Dialogues revealed a 12 per cent increase in this year's Budget was a roll-over of unspent funds from the last two years.
One of the report's authors, the Australian National University's Terence Wood, says this points to inefficiencies within the Ministry of Foreign Affairs and what he called Mr McCully's “capricious” management.
McCully dismissed the accusations, saying the aid budget works on a three-year cycle and it was not unusual for funds from very large multi-year projects to be carried forward.
"I have made it clear to the ministry that it is not important to balance the books at the end of the year. In terms of having an absolutely even amount of expenditure in relation to budget each year."
"We need to even it out over a period of years but make sure we are getting the best value for the dollars we spend across those projects," he said.
McCully hit out at the report's authors saying their observations pointed to a lack of understanding of New Zealand's aid budget process.
The authors however point out that there was also a significant carry-over of funds from the 2014/2015 budget year which was supposed to have marked the end of the last three-year budget cycle.
- RNZI