Hundreds of prisoners will be made to work fulltime and hit the gym, under government plans.

Prime Minister John Key said yesterday that three jails would be transformed into "working prisons" with 40-hour weeks of employment, training or rehabilitation for inmates.

Corrections Minister Anne Tolley said she wanted more prisoners in employment and education - and on exercise programmes.

"One of the worst things about being in prison is the boredom, sitting around doing nothing, and that's when people get into trouble," Mrs Tolley said.

"I would certainly like to see prisoners with their days full . . . so that when they hit their beds at night they are tired."

The scheme is already under way in Christchurch's Rolleston prison, which has a contract with Housing New Zealand to refurbish earthquake-struck properties.

Tongariro and Auckland women's prisons will also become "working prisons" this year.

Corrections already runs a bakery and pig farm and Auckland women's prison inmates work, stocking Corrections canteens.

"Each prison will be different in what they offer prisoners. But the idea is to have every single prisoner engaged in some work activity five days a week," Mrs Tolley said.

National wants to reduce re-offending by 25 per cent within five years. It plans to open up access to education, training and addiction treatment programmes.

Reoffending drops by 16 per cent among prisoners sent out on Release to Work programmes, and by 8 per cent among those who work in prisons, the Government says.

Mrs Tolley denied prisoners would be providing cheap labour for Corrections, pointing out that Release to Work participants get market wages.

Justice campaigner Kim Workman provisionally welcomed the plan, saying inmates often complained about "enforced idleness".

"One of the great myths perpetuated by some sectors of the community is that prisoners are by nature lazy and don't want to work. Most prisoners would enjoy the opportunity to work a 40-hour week," he said.

The proposal was outlined during the open session of Parliament yesterday.

Mr Key told MPs that this year would be challenging. "But the country is on the right track," he said.

The "working prisons" proposal was the only new announcement in the speech.

He reaffirmed a commitment to selling state-owned energy companies, and reforming the Resource Management Act.

Growing the economy would come by capitalising on The Hobbit films and focusing on free trade deals with Asia.

He also plugged the building of a convention centre in Auckland, which has been overshadowed by a controversial deal with SkyCity.

In foreign policy, the Government will ramp up its campaign to win a seat on the United Nations Security Council in 2015.

Mr Key went on the offensive over housing policy, attacking the Greens and Labour. The Government would cut red tape and build 2000 new homes, he said.

Labour leader David Shearer hit back, describing his rival's speech as "a joke".

Greens co-leader Metiria Turei criticised National's record on the environment and the economy.

- © Fairfax NZ News