The Government are working towards labelling common types of synthetic cannabis as a Class A drug "as soon as possible", however the Green Party are warning against a "costly war on synthetic drugs that is destined to fail".
"People who make synthetics are constantly changing the compounds and chemicals, it's impossible to know what's in these drugs," Green Party drug law reform spokesperson Chlöe Swarbrick said.
"If our plan is to classify every synthetic product then we’ll be playing catch up every time manufacturers change the chemicals."
"We can choose to carry on with a failed war on drugs, or take a more sensible route and look at the causes and health impacts of addiction and treat those instead."
It comes after Health Minister David Clark said making common types of synthetic drugs Class A "enables police to have greater search and seizure powers".
"We're aiming to do this as soon as possible."
National MP Simeon Brown welcomed the move, but said it did not go far enough.
"By only increasing the penalty for some synthetic drugs, dealers will avoid these penalties by simply changing the ingredients."
The Prime Minister said her Government needs to look at "all of the options that will make a difference".
"At this stage no decision has been made."