A serious violent or sexual offence will earn someone a first strike - or a warning.
A second strike means no parole, and for a third strike, offenders will have to serve the maximum penalty without parole.
Associate Justice Minister Nicole McKee said today the regime sends a message to those committing serious crime they will face increasingly serious consequences.
The Sentencing (Reinstating Three Strikes) Amendment Bill was among a raft of legislation debated under urgency in Parliament yesterday.
The government's new version tightens the legislation, lowering the qualifying sentence threshold for the first strike from 24 months' imprisonment to 12 months.