The campaign will run until June 8 and is part of a drive by the Home Office and the Association of Chief Police Officers to eliminate sales of alcohol to minors by 2007. It precedes Scotland's first test purchasing initiative, which is starting in mid-June.
The Association of Convenience Stores urged retailers to make sure their procedures to clamp down on underage sales were watertight. It called on them to enforce a 'no ID, no sale' policy for customers who looked under 21.
Government figures indicate the number of off-licences failing tests fell from 32% to 19% during the previous campaign.