Associate Health Minister Peter Dunne conceded that the latest move to declare two substances used in K2 illegal was something of a cat and mouse game for authorities, as others were brought into use.
"[That's] until we can deliver the killer punch in August when the Psychoactive Substances Bill will become law."
But the latest moves were a solid start, Mr Dunne said.
Last Tuesday Mr Dunne announced a Temporary Class Drug Notice banning the two substances found in tested samples of the synthetic cannabis. The ban comes into effect on Thursday and brings to 35 the number of substances banned under temporary notices - more than 50 products containing those substances are now off the market.
Submissions on the planned legislation closed on Wednesday and the Health Select Committee is due to report the Bill back to Parliament in mid-June.