When Katie Smith received £20 for Christmas, she knew exactly what she wanted to spend it on - a belly button ring.

Pop stars Britney Spears and Rachel Stevens have helped make navel piercings the latest must-have accessory for fashion-conscious girls.

So the 11-year-old secretly forged a permission note from her mother and went straight round to a piercing studio.

However, the ring soon became infected and Katie was forced to come clean to her mum Julie Swan.

Julie, 33, was furious when she heard. She was angry both with her daughter and the Green House studio in Imperial Arcade, Brighton, which undertook the piercing. She is now warning other parents about the risks.

Julie, of Firle Road, Brighton, said: "Katie had been asking me for months for a ring. She has been really keen.

"The reason I said no was because I don't believe in it anyway and she's not old enough to look after it.

"You have to constantly bathe it in salt water or TCP to make sure it has healed.

"Katie had her ears pierced when she was younger. But belly buttons are completely different.

"Apparently Katie wrote a letter and signed it herself saying she had my permission to have it done.

"It has become so badly infected I have had to keep her off school and taken her to the doctor."

The non-statutory British Body Piercing Association's code of practice and ethics states: "All associates, members and fellows of the association agree . . . not to give anybody a piercing under the age of 14 years."

Youngsters aged 14 to 16 must be with an adult.

But Julie said she had spoken to the piercing parlour and Brighton and Hove City Council and was told there had been no wrongdoing.

She said: "I am in a situation where my 11-year-old daughter has had this done, got infected and there's nothing I can do about it. I'm absolutely livid."

Owner Robert Green said: "We usually phone up to check if people have consent. But this was a forged note and looked quite genuine.

"Everyone is given an advice sheet but this only became infected because she did not look after it properly.

"We have offered to compensate the lady if she brings the jewellery back and will look after it until it has healed."

Mr Green said the studio was registered with the council.

A council spokeswoman said: "Ear piercers, tattooists and acupuncturists have to be registered but body piercers do not.

"But the law is changing and body piercing studios will have to be registered with us by April 1 and be licensed like any other establishment.

"New Government guidelines are also coming in in February and, as soon as these are released, we will be setting up an accreditation scheme."

Last year, actor Christopher Ellison grounded his 13-year-old daughter Francesca after she was able to get her belly button pierced without his consent, also at the Green House.