May 9 - Some clothing firms in the United States are marketing sexy garments for pre-teen girls, reinforcing a destructive stereotype of female attractiveness, research released on Monday said.

Piece from Pitti Bimbo's Spring Summer 2011 collection. Photo - Pixel Formula

Girls as young as six are being pitched clothing that highlights their breasts, buttocks or slimness or sends a message of sensuality, the study says.

Researchers led by Sarah Murnen, a professor of psychology at Kenyon College in Ohio, looked at 15 websites of popular clothing stores, ranging from bargain to high-end sectors of the junior US market.

Using 38 college students, they devised a system to assess the sexiness of various garments, and used this system to grade 5,666 clothing items.

Clothing was rated according to whether it had only childlike characteristics; revealed or emphasised an intimate body part; or had characteristics that were associated with sexiness.

An example of a "childlike" characteristic would be a top with a butterfly print in pastel colours.

In contrast, a bikini was coded as "revealing" because it exposed the waist and part of the chest. The bikini was considered "emphasising" if, for instance, it outlined each breast with triangular pieces of fabric.

Similarly, highly-decorated back pockets on trousers -- adorned, for instance, with a bird or sequins -- were deemed "emphasising" because they drew attention to the buttocks.

Material that was lingerie-like (such as in slinky red or black fabric) or in leopard or zebra prints was categorised as having characteristics associated with sexiness.

Sixty-nine percent of the clothing assessed in the study had only child-like characteristics.

Four percent had only sexualising characteristics, while 25 percent had both sexualising and childlike characteristics. One percent had neither sexualised nor child-like characteristics.

The researchers said the biggest sexualisation was in clothing sold by "tween," or pre-teen stores, especially Abercrombie Kids, which came under fire in 2002 for selling thong underwear in children's sizes with "wink wink" and "eye candy" printed across the front.

The paper appears in a specialist journal, Sex Roles, published by Germany's Springer publishing house.

Its authors say girls face escalating demands placed to meet the Western stereotype of slimness and sexiness. The pressures of "self-objectification" can lead to body dissatisfaction, depression, low confidence and poor self-esteem.

"The co-occurrence of sexualising and child-like characteristics makes the sexualisation present in girl's clothing covert," it says.

"Confused parents parents might be persuaded to buy the leopard-pink miniskirt if it's bright pink. Clearly, sexiness is still visible beneath the bows or tie-dye colours."