A group of Nottingham e-cigarette retailers have been caught selling to children in a test purchasing operation.
A total of eight stores from 14 chosen from across the city failed the checks, Nottingham City Council said.
It became illegal to sell nicotine products such as e-cigarettes to under-18s on October 1, with those ignoring the new law liable to be fined up to £2,500.
But the city council said the offending retailers have all been issued formal warnings and told to expect fines if caught again.
Councillor Nicola Heaton said: “Our trading standards service treats the welfare of young people as a priority and regularly take action against sellers of age-restricted goods to children.
“Nottingham city retailers must ensure that they sell these products only to people who are old enough to buy them, or prepare to face the consequences.”
The operation, carried out at the end of October, involved child volunteers going into shops and asking for items including e-liquids with nicotine in them. The council did not name the shops involved.
Other age restricted products were included in the test purchase operation, which caught businesses selling fireworks, two sales of alcohol and one business selling illicit cigarettes to children. The council said “investigations are continuing” into these sales.