Key Points:

The Government's military-style "boot camp" legislation will target New Zealand's young "ticking time bombs", Prime Minister John Key said today.

He said the legislation, to go before Parliament on Wednesday, will send a strong message the behaviour of New Zealand's worst young criminals would not be tolerated.

The policy is a favourite of Mr Key, who raised it in his state of the nation speech a year ago, and the bill will get its first reading as part of National's 100-day plan.

It includes the Fresh Start programme - lasting 12 months, including up to three months in boot camp - and the doubling of youth court sentences.

It also extends the Youth Court's jurisdiction so it can deal with those aged 12 and 13 accused of serious offences.

Mr Key said that 40 of the country's worst offenders will take part in military style training programmes for three months.

"We need to deal more effectively with the growing group of young Kiwis who are seriously and repeatedly breaking the law. These ticking time bombs need to be sent a message that their behaviour will not be tolerated," Mr Key said.

Social Development Minister Paula Bennett has previously said some of the changes will not be available until next year, to allow time to set up the programmes, or have the space in residential centres to house those sentenced.

Other measures - including greater use by the Youth Court of orders for alcohol and drug rehabilitation, mentoring and parenting courses - would be available sooner as no law change was required.

The legislation is also expected to include "spotlight sentences" - where young offenders who do not comply with supervisory sentences are subject to monitoring with an ankle bracelet.

In his speech, Mr Key said spotlight sentences would be a court-ordered contract setting out the expectations on the offender such as curfews, an end to gang involvement, compliance with drug treatment programmes, or regular school attendance.

Mr Key said that to ensure compliance the court would "wield a big stick" - "intensive supervision and surveillance, including electronic monitoring of the young person using an ankle bracelet".

The Act Party's "three strikes and you're out" legislation will also go before Parliament this week.

Under the policy, criminals convicted of a serious offence for the third time will be sent to prison for a minimum of 25 years.

It is being introduced to Parliament by National as part of its support agreement with Act, although National has agreed to support it only to the select committee stage.

Act leader Rodney Hide said it was pleasing to see the policy make it in under National's 100-day plan.