Interim changes will be made to clamp down on synthetic cannabis before more substantive changes come into force, says Associate Health Minister Peter Dunne.

Auckland Chamber of Commerce chief executive Michael Barnett wrote to MPs raising his members' concerns about the products and about how slow Parliament's response had been.

Legislation was urgently needed to require manufacturers to prove their products were safe before they could be sold, he said.

Labour MP Iain Lees-Galloway backed the call.

"The public is rightly demanding the Government moves now to set up a mandatory proof of safety regime around these drugs," he said.

"That means when Parliament next sits, not next year as Peter Dunne has signalled.

"There is no reason meaningful stopgap measures can't be implemented immediately. We are testing these drugs on our young people. That is shameful and it has to stop."

Mr Lees-Galloway also called for a revision of the Misuse of Drugs Act in the long term.

Mr Dunne said he shared the chamber members' concerns.

"We have already indicated that strong additional amendments to the Misuse of Drugs Act will be the first item of business when Parliament sits again next week and those amendments will deal with synthetic cannabinoids and other legal highs," he said.

"They will be introduced by way of supplementary order paper at the committee stage of the legislation and I believe they will meet with strong approval."

Next week's amendments would be an interim step before the Government could legislate to reverse the onus of proof so the synthetic cannabis industry would have to prove its products were safe before they could be sold, Mr Dunne said.

"The Government has backed this Law Commission proposal and is now working to put a regime in place."

At present, products must be proved unsafe before they are pulled off shelves.

That happened most recently when a brand of the popular synthetic cannabis product Kronic was banned by the Director-General of Health because it contained the prescription medicine phenazepam.