The Government's keeping its cards close to its chest  on how it'll fund a mammoth defence splurge.

It's injecting $12 billion over the next four years into building up our Defence Force workforce and equipment. 

It's signalling it'll go into system upgrades, replacing helicopters - and enhancing maritime strike capability.

Defence Minister Judith Collins says the investment includes $9 billion on top of what we already spend on defence.

"It is a lot of money, but I also know this - there is no economic security without national security." 

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