Young secret shoppers in Devon are to help stop pubs and off-licences selling alcohol to underage drinkers in the run up to the World Cup.
Alcohol was sold to children as young as 14 in other operations
Police and Trading Standards officers will work on the operation at a time when licensees expect increased trade.
In December, a similar swoop found 44% of premises targeted were willing to sell alcohol to buyers as young as 14.
Meanwhile, staff at three pubs in Cornwall have been fined £80 each for serving underage customers.
The operation in Devon is expected to be the first of two to take place this year as part of the government's alcohol misuse enforcement campaign.
Sgt Dave Elliott of Devon and Cornwall Police said: "Irresponsible consumption of alcohol is a generator of crime and disorder. In recent years, the amount of alcohol 16-year-olds drink has more than doubled in the UK.
"Ongoing enforcement action such as this campaign is one of a range of measures which we are employing to address this problem."
Although it will primarily target pubs and clubs, some off-licences and supermarkets will also be checked.
Cllr Roy Connelly of Devon County Council said: "Supervisors and licensees in all types of licensed premises need to ensure they have effective systems in place to prevent underage sales.
"They need to make sure that every member of staff responsible for alcohol sales is prepared to challenge youngsters to prove their age."
In Cornwall, staff at three pubs in Saltash and Callington in Cornwall have been fined £80 each for serving youngsters as a result of undercover visits.
Police visited 15 pubs and off licences over the weekend in the towns.
They were accompanied by officers from Cornwall's Trading Standards department, as well as young people who posed as customers.
Police said although they were disappointed three pubs had served the youngsters, they were confident the licensees would learn their lesson.
They also said it was encouraging that the other 12 premises were completely responsible in refusing to serve the children.