The former Minister of Defence has admitted he "completely forgot" about a report which stated civilian casualties were possible during Operation Burnham.
The Burnham Inquiry, led by Sir Terence Arnold and Sir Geoffrey Palmer, has found a child was killed during the operation in Afghanistan and at least seven men also died - three of whom have been identified as insurgents.
The two-year investigation found New Zealand Defence Force (NZDF) officials did not plot to cover-up the casualties from the Operation in August 2010, as claimed in the book Hit and Run by investigative journalists Nicky Hager and Jon Stephenson.
It did, however, find the Defence Force never corrected claims made to the public and ministers by its personnel that allegations of civilian casualties were "unfounded", despite knowing it was possible.
The Burnham Inquiry stated NZDF officials mislead former Defence Minister Wayne Mapp for more than a year as to the possibility of civilian casualties.
But Mapp continued to tell the public claims of civilian casualties were not true after receiving a briefing which said they were in September 2011, it said.
Mapp told RNZ he likely forgot about the briefing because of the death of New Zealand soldier Leon Smith, which happened at about the same time.