In a surprise attack, Sir Stephen House claimed the requirement to demand drinkers who look under 25 produce identification before they are served "has not seen any reduction in the consumption of alcohol by children and young persons".
Instead, Sir Stephen has claimed the Challenge 25 scheme, introduced as law nearly three years ago, has simply shifted the problem elsewhere, with more adults buying drink for youngsters.
The Police Scotland chief constable said: "There is a move towards agent purchase of alcohol and much less instances of children or young persons purchasing alcohol themselves."
Sir Stephen made his intervention in a report to all of Scotland's councils in which he offers an overview of other policies such as test-purchasing of alcohol by children under 16 and bottle marking schemes.
Police Scotland said it was determined to report adults purchasing drink for under-18s to prosecutors, while the Scottish Government has promised to tighten the law around adult purchases.
Challenge 25 was introduced as part of the Alcohol Etc (Scotland) Act 2010, as part of legislation which also included banning off-sales and supermarket promotions such as six cans for the price of four or three bottles of wine for £10.
As a result of the change in the law, customers in any premises, including pubs, clubs, restaurants, supermarkets and convenience stores were to be asked to produce identification if they appeared to be under the age of 25 to prove that they were over 18, while the Scottish Government said Challenge 25 meant staff were less likely to make a mistake.
John Lees, of the Scottish Grocers' Federation, said retailers had made Challenge 25 "a highly effective age restriction policy".
However, he added: "It is clear that proxy purchases are now the main factor in under-age drinking.
"Enforcement now has to shift outwith the store to focus on what happens in the wider community and in the family. In our view this can only be done through targeted, locally-based projects such as Community Alcohol Partnerships, whole of population approaches are becoming less and less relevant."
A spokesman for leading charity Alcohol Focus Scotland said: "Policies like Challenge 25 can only be effective if they are implemented as part of a multifaceted approach to reducing alcohol harm. Reducing the affordability, availability and marketing of alcohol are recognised as the three most effective ways of tackling alcohol harm and will have far more impact on protecting young people."
Sergeant David Macdonald, of Police Scotland, said: "Young people are obtaining alcohol from adults who may buy on their behalf or even taking alcohol from their homes. Where police officers find children and young people in possession of alcohol they will conduct enquiries to find the source and take relevant action. This could include tracking down irresponsible adults who may be reported to the procurator-fiscal for supplying alcohol."
A Scottish Government spokeswoman said recent evaluation found Challenge 25 was welcomed as a tool for restricting the sale of alcohol to young people.
He added: "We recognise the problem of over-18s buying alcohol on behalf of those who are underage. The upcoming Licensing Bill is expected to make it an offence to supply alcohol to under-18s in a public place."