The Girl Power magazine's December 2008 issue, targeted towards girls aged 7-13, directed them to a fashion-oriented site, which has a forum where older girls discuss pregnancy fears, anorexia and explicit sex acts.
The parent groups have expressed concerns over the unregulated content of the tween magazines.
Some of the magazines read by children as young as six urge kids to buy expensive adult perfumes and makeup.
It also sways them to have the latest "look" with detailed fashion spreads and beauty advice.
Some of the magazines also advertise products for small children and offer advice on boys.
Because of the lack of regulation, the Classification Board can only act if it receives a formal complaint.
Kids Free 2B Kids director Julie Gale said that the effect was insidious.
She said that tween magazines forced readers to grow up too quickly and "could very well impact on the mental health of the young girls reading them," reports the Daily Telegraph.
The Senate inquiry heard numerous concerns about magazines directed at young girls.
Instead of implementing a rating system, it suggested reader advice on the cover about content, "indicating the presence of material that may be inappropriate for children". (ANI)