A government bill overhauling drug laws passed its first reading in Parliament this evening.
The Misuse of Drugs Amendment Bill seeks to classify the two main synthetic cannabinoids as Class A drugs, and affirm police discretion over whether to charge people with possession and use of drugs.
National Party MPs told Parliament the bill raises the threshold for arresting and charging people with drug crimes and they will oppose it.
National MP Chris Bishop told Parliament the bill's approach to discretion would essentially make the police responsible for decriminalising drug use.
"What the government is doing, is subcontracting out to police officers decriminalisation. My message to the government is if you want to have a debate about drug decriminalisation and if you want to have a debate about making sure that people who are addicted to heroin are not prosecuted, maybe there's a role for that debate."
Labour Party MPs said police already exercise discretion over drug prosecutions and the bill will encourage them to take a health approach to dealing with addicts.
The bill will now be considered by the health select committee.