The 'Shop a Shop' scheme launched in the borough of Brent this month. Anyone who has information on the sale of tobacco, alcohol, knives, fireworks and adult DVDs to under-18s is being encouraged to text the word SHOP to 80800, followed by a description of the store and how they believe it is breaking the law.
The free-to-send messages will be examined by staff at Brent and Harrow Trading Standards, who will then conduct test purchases on any named stores.
Brent and Harrow Trading Standards director Peter Kendall said the scheme would "speed the flow of information about illegal sales", but denied it could be abused by disgruntled teens who had been refused a sale. "Responsible retailers who take appropriate care not to sell age-restricted products to under-18s have nothing to fear," he said.
Other local authorities would be following the scheme with interest, Kendall added.