A person has died in Christchurch after taking synthetic cannabis, which has swiftly prompted calls for a crackdown.

Two people remain in ICU after 19 people have been admitted to Christchurch Hospital over the past two weeks after using the substance.

The drug has also been linked to numerous deaths in the North Island in the past year.

Police Minister Stuart Nash says it's a matter of life and death, and they are taking it seriously.

"Health, Corrections Customs and Police are all working on a number of initiatives, and changes are on the way."