The government's spending about $1b adding extra beds in prisons throughout the country.

None of the 1800 new beds are being allocated to the Otago Corrections Facility.

At the last count in September there were 465 prisoners at the Milburn jail.

They made up just under 5% of the country's total inmate population.

There are currently almost 10,000 prisoners nationwide and the government says that number's growing faster than expected.

Double bunking is being increased in Northland, a new block will be built at Mt Eden, and the Waikato's new jail is set to be expanded.

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