The father of an underage teen who illegally bought a bottle of vodka online is looking to bring a private prosecution against supplier The Mill.

Gavin Holmes reported his 17-year-old son's purchase of a $29.99 bottle of Red Square Vodka to the police in November after he was unsatisfied with The Mill's response to his complaint. All the boy had to do to buy the booze with his debit card was tick a box which said he was over 18.

Holmes took delivery of the vodka at his Hamilton East home when his son was out and, suspecting it was alcohol, asked him to open it in front of him when he got home.

He then confiscated the bottle.

Police required the retailer to change its website after Holmes' complaint by asking visitors to fill in their date of birth before going ahead with a purchase.

"The police are not proceeding with prosecution," Holmes said yesterday.

"The police do seem to be fighting this with both hands tied behind their back. Surely it's as simple as being illegal to supply alcohol to a minor and they have done that. If the alcohol was sold in a traditional face-to-face situation, they would get done.

"They should be done for the sale of alcohol to an underage person and I am looking for a lawyer to take the private prosecution on pro bono."

Holmes has suggested online shoppers be required to register a free RealMe account.

The Mill Retail Holdings chief executive Jeremy Livingston did not respond to a request for comment.