Opposition leader Christopher Luxon plans to get tough on gangs and repeat youth offenders if National gets into power.
Luxon announced National's commitment to "restore law and order" during a state of the nation address on Sunday.
He said National would back police and tackle gangs, making it harder for them to access firearms, and ban gang patches in public places.
Luxon said National would also introduce military academies for repeat youth offenders.
"And we'll introduce tough consequences, including youth military academies, for serious, repeat youth offenders because we want to help them turn their lives around."