He described it as a "disgusting act of dishonesty" which had affected the tourists' travel plans.
Police are now calling for any information that could lead to the identity of the offenders or the recovery of the tourists' property.
The car's driver a passenger were described as male Caucasians with brown hair, both of whom were smokers. The vehicle was a grey four-door sedan with a registration plate starting with 'C'.
One of the backpacks was a blue Osprey-branded 75-litre pack covered by green rain cape.
The other was a red Deuter-branded 65-litre pack with a blue rain cape.
Anyone with information could contact Waikato police on 07 858 6200 or the Crimestoppers organisation, anonymously, on 0800 555 111.