The man behind a controversial $2.75 million Mongrel Mob-led drug rehab programme has a message for his critics: "Jacinda seems to trust me. Why wouldn't you?"

Hard2Reach director Harry Tam, a lifetime honorary member of the Mongrel Mob behind the Kahukura programme under way in Central Hawke's Bay, appeared on TVNZ's Q+A on Sunday to explain why rehab was so badly needed in gangs.

Kahukura has turned into a political football in recent days after Hawke's Bay Today revealed the programme for Mongrel Mob members had received nearly $3m from the Proceeds of Crime Fund.

It is based on a marae at Tapairu Marae, outside of Waipawa and involves Sonny Smith, a Mongrel Mob leader who lives in the area, and his wife Mahinaarangi Smith.

Tam, who has spent much of his life in the public sector, told Q+A that methamphetamine didn't finance gangs, in his experience at least, but rather individuals within gangs.

"People get into selling meth initially to support their own habit then they realise they can make quick money and big money and then they go on and on."

He said cutting off supply was important, but so was reducing demand.

"I think a lot of our strategies have been focused on reducing supply, which I don't disagree with, but we also need a balanced approach," Tam said.

"This is just market theory isn't it? If you reduce the demand there's no need for supply."

Tam said the people who joined gangs and were ravaged by addiction had often suffered abuse in state care.

"You only have to have a look at what's coming out of the Royal Commission of Inquiry you know where … gangs originated from in New Zealand. It's the people that have been in state care and have been abused and their traumas have never been dealt with.

"So, it's an intergenerational transfer of trauma and dysfunction."

He told Q+A the best way to deliver drug programmes is using people gang members knew well - those outside normal societal structures.

"A lot of our people don't trust people … and if you look into their backgrounds they've got good reasons not to trust authority. A lot of people have been institutionalised most of their lives.

"We often assume that you know, you can just rock on up and say; 'Hey bro, I wanna put you through rehab.' And it'll be 'Piss Off.' But, if it's somebody that [they] can trust that comes in there and has the conversation, you'll be amazed what comes out.

"People want change, but they don't know how to change."

When asked about how he was perceived because of his Mongrel Mob title, Tam said:

"My loyalty lies in being a good New Zealander ... Jacinda seems to trust me. Why wouldn't you?

"It doesn't matter what I do, because I've had that label, you don't trust me.

"It doesn't matter what references I've, you're still going to look at me and say he's one of them."

Tam said Muldoon was one of the only NZ Prime Ministers that had actually engaged with gangs and helped put them to work, but people wanted to sweep that under the carpet.

The Muldoon era ended and NZ then moved into a search and surveillance era, which had now lasted 30 years and caused significant harm, Tam said.