The Drug Foundation is welcoming a law change requiring legal high manufacturers to prove their products are safe before they can be sold.

Associate Health Minister Peter Dunne announced on Monday that the government will introduce new legislation reversing the onus of proof on party pills and synthetic cannabis products.

The law will require their producers and distributors to provide toxicology data and results of human clinical trials to a regulatory body, which will declare whether they are safe before they can be sold.

Currently, the government is able to temporarily ban specific ingredients in the products with 12-month temporary class drug orders, which classify the substances as the equivalent of Class C1 drugs.

However, the orders are issued only after new products arrive on shelves.

"The new law means the game of 'catch up' with the legal highs industry will be over once and for all," Mr Dunne said.

The first orders, which came into effect in August last year, are about to expire but will be extended for a further 12 months.

Drug Foundation executive director Ross Bell says the law change will bring the country's "obsolete" drug law up to date.

"Unknown and untested new synthetic substances have been hitting the shelves for a decade in New Zealand. Consumers have simply never known whether these drugs are safe or not," he said.

"It makes sense that the industry should have to jump through hoops to prove its products are safe before they go on sale."

The law change will also establish a new regulator, similar to the government's medicine safety regulator Medsafe, in the Ministry of Health to assess the safety of the products.

Product manufacturers will have to bear the cost of the assessment, which is expected to total $1-2 million annually, Mr Dunne says.

There are also likely to be restrictions on purchase age and where the products can be sold.