A boy of 15 was caught running a tattoo parlour from his bedroom in Blackpool by Trading Standards officials.
The illegal operation - which the lad advertised on Facebook - came to light when the parents of a 14-year-old girl complained when she arrived home with a tattoo on her leg.
Trading Standards officials then discovered that children as young as 13 had been inked with butterflies, hearts and swallows by the youth for just £5 a time.
They found his stained and contaminated tattoo kit hidden beneath his bed along with a magazine called Tattoo Ideas, rubber gloves and tracing paper.
The officers confiscated the equipment but after being questioned on suspicion of an offence under the Tattooing of Minors Act, the teenager was let off with a warning.
In Britain it is illegal to tattoo anyone under the age of 16, and only legal for 16 to 18-year-olds to be tattooed with their parents' consent.
The maximum sentence for tattooing a youngster under the age of 16 without parental consent is a fine of up to £1,000.
The 15 children who were tattooed by the boy are now being urged to visit their GP amid fears over the risk of hepatitis from lack of hygiene and his apparent attempts to 'sterilise' the equipment with household detergents such as Dettol.
Councillor Fred Jackson, of Blackpool Council, told Click Lancashire that he was 'shocked' at the risks young people were prepared to take with unregistered tattooists.
"I understand that the equipment can be bought from as little as £50 on eBay, making it more accessible than ever to those wanting to make a quick buck," he said, "The last thing we want is young people making a bad decision that could cause permanent damage and impact on their health."
Blackpool Council has launched a campaign with the Blackpool and Fylde College to raise awareness of illegal tattooing after a series of similar incidents.