TVNZ is heightening its ambitions as its main competitor is put up for sale.

The state-owned broadcaster is amping up its reality TV and local shows, in an effort to compete with international streaming services.

It comes after MediaWorks announced it's looking for a buyer for its TV3 and Bravo channels.

TVNZ CEO Kevin Kenrick told Mike Hosking it's a tough business, but they're going all-in.

"The state of the current market is unsustainable, so some things will have to change. We have elected to invest to build a future."

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