The legal age to buy alcohol in New Zealand is 18.
Mr Clement said when applying for a licence, all applicants state they have appropriate systems and procedures in place to stop the sale of alcohol to minors.
But that clearly was not the case for the premises that sold alcohol to the two underage volunteers, he said.
"I would like to emphasise to all sellers, that anyone attempting to purchase alcohol who looks under 25 years of age and unable to produce identification, do not sell the alcohol to them. It is important to stress that a full and proper identification check must be carried out including calculating the age. This is best practice and the only sure way to prevent sales to those underage."
Mr Clement said the consequences when the licensees are reported to the authorities are significant.
He said there were financial implications and there was likely to be a period of suspension of the licence. He said this will affect the business and the managers.
"All premises selling or supplying alcohol are well aware that we run these types of operations regularly so should not be surprised that they are being tested."
Controlled Purchase Operations are part of an ongoing programme to assess compliance with the Sale and Supply of Alcohol Act 2012 in an effort to address access to alcohol by minors.