Asda has unveiled measures to limit access to alcohol in its stores and make it harder for under-18s to break the law.
The supermarket chain will also stop selling alcohol between midnight and 6am in town centre stores in an effort to prevent late-night revellers from purchasing more booze.
The grocer is to extend its Challenge 25 proof of age scheme to 100 more stores, following a successful pilot in Scotland.
Asda will also invest£1 million in targeted youth projects to tackle alcohol-related problems among children, working alongside Business in the Community.
Asda chief executive Andy Bond said: “As a parent myself, I find it unacceptable that children in the UK are still able to purchase alcohol from retailers and pubs. So, from today, we are adopting a zero-tolerance approach.
“Every single Asda store in the UK will be independently tested at least once a month, with the results published on our web site. We will also display signs within the store making it clear that we reserve the right to prosecute anyone under 18 who attempts to purchase alcohol or anyone that is doing so on a child's behalf.”
The initiative comes after supermarkets came under pressure last week from the Government to make alcohol less accessible.