Peter Dunne's landmark legislation to ban unsafe synthetic cannabis and party pills remains on track despite his exit as a minister.

Rotorua MP Todd McClay takes over Mr Dunne's revenue and associate health roles today after the United Future leader resigned them amid allegations about his role in the leak of a confidential GCSB report.

The Psychoactive Substances Bill - one of United Future's main initiatives - would not be affected by Mr Dunne's demotion, Mr McClay said, and he expected the legislation to pass next month.

"I've asked for a briefing from officials pretty quickly and I think it's important that we get the bill into law as quickly as possible so that we can have a regime that creates certainty and protects young New Zealanders."

Prime Minister John Key indicated the Government would continue to support United Future initiatives outlined in its confidence and supply deal with National.

Those include Flexi Super and income-splitting tax plans.