The parents of a Masterton teenager who died after taking drugs and being given a potentially fatal dose of methadone, say the supplier should have been convicted of manslaughter.

Instead Daniel George Ewen, 38, was today sentenced to two years jail for supplying Aaron Richard Miller, 17, with methadone.

Ewen was prescribed methadone to help with his addiction to opioid-type drugs.

In the High Court at Wellington Justice Ron Young said although the manslaughter charge was not proceeded with, so Ewen was not found legally responsible, he should feel responsible for Aaron's death.

Aaron died last October 18.

After the sentencing Aaron's parents Shaun Miller and Linda Murphy said they thought Ewen should have been convicted of manslaughter and the dropping of that charge had been a shock.

They thought the sentence was too short.

Aaron had been with a small group including Ewen's teenage son who had visited Ewen's home and were drinking alcohol.

Justice Young said that during the evening Ewen's son and Aaron went to Miller's room where Miller withdrew a portion of liquid methadone with a syringe and gave it to Aaron who squirted it into his mouth.

Aaron left soon after and was found dead in the morning.

A toxicology report found Aaron had been given a potentially fatal amount of the drug and had died from the toxicity of a combination of the drugs and alcohol, the judge said.

Initially Ewen lied about supplying the methadone but admitted giving Aaron other drugs in the past.

Ewen has said that he was hounded into supplying the methadone but Justice Young called that "nonsense"

"It is nonsense to suggest you were in any way forced to supply this methadone, you did so entirely voluntarily."

"Your actions frankly were beyond irresponsible."