He also referred to a letter from the former Defence Minister Ron Mark on October 5 who said "the airfield could potentially be used by New Zealand Defence Force fixed-wing aircraft if Wellington Airport was unusable.
"In that case, transporting personnel and/or supplies into and out of Kāpiti would save approximately one hour by road from Ohakea."
Gurunathan also cited an incident involving former Prime Minister Helen Clark and the "saving grace" of the airport.
In April 2005 Clark and some others were on a small aeroplane that had taken off from Wellington Airport when turbulence struck at 8000ft, causing a door to burst open.
"While two police officers grappled with the door the plane avoided being ditched into the sea and landed safely at Kāpiti Coast Airport.
"A bruised and shocked Helen Clark later told media she had feared for her life.
"I recall this incident to point out that Kāpiti Coast Airport maintains a day-to-day emergency alternative for fixed-wing planes flying across the turbulent Cook Strait and as an alternative airport.
"In particular, for the Emergency Aeromedical Retrieval Service operating out of Wellington Hospital's intensive care unit."
Gurunathan said to Ardern: "There doesn't seem to be a clear and comprehensive direction on the role of Kāpiti Coast Airport in the context of a regional emergency.
"The responsibility of ultimately recognising that role, or clearly discounting that role, rests with you and your government and not with my council nor the private airport owners."
Kāpiti Coast Airport was sold by Todd Property Group to NZPropCo late last year.
Templeton Group, which is the main part of NZPropCo, is reviewing all aspects of the airport's ongoing operation sparking fears it could close.