The First Minister says the Conservatives deal with the DUP is unacceptable.
Children Treated For Drug and Alcohol Abuse
Children as young as four are being treated for substance problems.
A Freedom of Information request has found hundreds of children of primary school age are at risk of becoming addicts.
In Wales, the youngest was a 10 year old from Monmouthshire.
11 year olds in Caerphilly and Blaenau Gwent have also been helped - as well as a 14 year old in Flintshire.
Experts say children often experience their own substance issues if their parents have a problem with drugs or alcohol.
The UK's leading drug and alcohol charity Addaction says it's vital preventative work is carried out to head off the problem of child users.
It also wants to see better drug education in schools and for teachers to be able to spot the signs of potential drug or alcohol abuse.
Mr Haines said: "In reality, a lot of young people don't feel comfortable to tell their teachers or to tell their peers whether it's their own substance misuse or parents, they're going to try and hide that. It's not something that is easily detectable - until there's a crisis."
He added warning signs can be wide and varied. Performing poorly at school, signs of a mental health problem and signs of physical abuse or neglect are all potential signals.
Up to 5 million pounds is spent in Wales on drug prevention work aimed at young people as well as providing support services for those who need help.
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