About 100 people gathered in Dunedin's Octagon this afternoon to protest legal highs.

Protests are being held in 23 centres from Whangarei to Invercargill today, and they were organised by Tokoroa mother Julie King via a Facebook event page, "Aotearoa bans the sale and distribution of legal highs in our country".

One of the speakers at the Dunedin protest was Calvin Hooper, who protested outside Cosmic Corner in George St earlier this week after his son was admitted to Wakari Hospital following synthetic cannabis use.

Others included Dunedin protest organiser Karen Casey, concerned parent Wayne McFadyen, and Dunedin South MP Clare Curran.

Protesters planned to picket stores selling synthetic cannabis this afternoon.

In Rotorua, two shops licensed to sell synthetic cannabis closed their doors early today to avoid protesters taking part in the nationwide protest.

Wild Things and Skingraft were on the march route from Kuirau Park to City Focus via Pukuatua and Tutanekai streets.

Around 300 people took part in the march, with babes in arms through to grandmothers and grandfathers and from every facet of the Rotorua community.

"Synthetic cannabis is reaching right into our communities, into our houses and families," said organiser Maraea Pomana, a youth worker with Te Waiariki Purea Trust.

"We're tired of seeing a family in strife and struggling, we're tired of seeing family violence. To have synthetics legalised is our last straw. This comes from all over our social networks, our hapu and young people. We're tired of it and we don't want another addiction for our whanau."

The march included Rotorua MP Todd McClay, Rotorua District councillors Charles Sturt, Merepeka Raukawa-Tait and Tania Tapsell.

Mr McClay spoke at City Focus.

"It's the people who have these licences who are selling this stuff are the people who are causing harm," he said.

"Here in Rotorua there were 20-30 outlets, today there are four and we know where they are. I say to those people, listen to the voice of our community, send your licences back on Monday, you do not need to sell these products."

Submissions for the council's Local Authority Policy regarding the rules for businesses licensed to sell synthetic cannabis products, were presented to Deputy Mayor Dave Donaldson.