Speaking on Newstalk ZB on Wednesday, King questioned the link between alcohol and suicide.
"Alcohol is not a problem for people with mental health issues. It's actually the solution to our problem, until you come up with a better solution," he said.
"I would suggest to you that alcohol has prevented more young people from taking their own lives than it actually takes their own lives."
King immediately defended his reasoning, saying he had used drugs and alcohol to "stop that little voice inside my head" and that it was a "release" and a "lifejacket" until he got counselling.
Drug Foundation executive director Sarah Helm said King's comments were "really unhelpful".
"I'm really worried about this message and the harm it might do, particularly for young people. Those of us who have a voice in the community and a role like this, our voices are very important and can have really significant consequences.
"These statements in particular go against the hard work of many people over successive decades to try and build awareness around mental health and suicide prevention, so yeah really concerned and also feeling for those many New Zealanders who have lost loved ones to alcohol-related suicide today."
People should reflect on how harmful it was to reach for the bottle during times of significant distress such as a relationship break-down, she said.
"One of our team members is involved in the Child Youth and Mortality Review Committee and you know they've seen many situations where a group of people were drinking during a situation like that, they left the person in what they thought was a happy state and it's ended in a fatality."
Alcohol and suicide were very closely linked, she said.
Although Mike King suggested that alcohol could be helpful for people with mental health issues, Helm said "alcohol was really unhelpful during times of mental distress", she said.
Labour is calling on the government to pause its funding of I Am Hope/Gumboot Friday, following King's comments.
The government has funded $24 million towards King's Gumboot Friday initiative, over the course of four years.
Labour's mental health spokesperson Ingrid Leary said that should be reviewed.
"The comments are deeply problematic and fly in the face of well-established body of literature that links alcohol use both directly and indirectly with mental ill health, including with suicide risk," she said.
"To continue to fund Gumboot Friday sends a message to young people that alcohol use is a recognised treatment for mental health issues."
Helm said she did not want to get into the political debate of whether or not the charity supported by Mike King should receive government funding.
"What I would say is that our addiction and harm reduction sector is very under-funded and is constantly struggling and I would focus my comments more on needing to resource that properly than reflecting on resourcing for his organisation."
Asked whether any of what Mike King said with regards to alcohol was true, Helm said the part that was true was that people often turned to alcohol and drugs during times of mental distress.
"But it's very dangerous to describe it as a solution."
King said that using alcohol was akin to having a life jacket or using methadone, but Helm said although opioid substitution therapy using methadone was very well evidenced, it could not be compared to drinking alcohol.
"Big fan of moderation messaging and careful regulation of alcohol but I think the comparison to methadone is appalling."
A lot of people in the addiction prevention and mental health sectors would now be trying to correct the messages put out by King, she said.
The minister for mental health, Matt Doocey, said he had a lot of respect for King and the work he had done for young New Zealanders, but he disagreed with his comments.
"Excess alcohol consumption can cause a lot of harm in our communities, that is why this government is taking alcohol harm seriously," he said.
Doocey said he was committed to ensuring people had access to appropriate alcohol and other drug addiction services, and that substance use was treated as a health issue.
He defended the government's funding of I Am Hope, which would provide counselling services to five to 25 year olds.
"My interest remains with the additional 15,000 young New Zealanders a year who are able to access free mental health support due to the funding that has been provided."
The procurement process for the funding, part of National's coalition agreement with New Zealand First, has come under the spotlight.
Earlier in October, the Auditor-General criticised the process, saying the contract was "inconsistent and unusual" and that the funding was to a specific supplier rather than to a broad policy initiative or to achieve a policy outcome.
Leary said King's latest comments added fuel to the fire.
"It must be galling for the many wonderful non-governmental organisations with safe and evidence-based approaches to providing mental health support and services to hear these comments, and know that they weren't able to contest for these funds and help these young people," she said.
Mike King declined Checkpoint's request for an interview.