San Francisco  - One in five teenage girls say they have electronically sent, or posted online, nude or semi-nude images of themselves, according to a survey released Wednesday.

The sleazy images are widely passed around, according to the survey of 1,280 teenagers and young adults by the National Campaign to Prevent Teen and Unplanned Pregnancy and CosmoGirl. com.

A third of teenage boys and a quarter of teenage girls said they had nude or semi-nude images - originally meant to be private - shared with them.

Though 73 per cent of young people acknowledged that such actions could have serious negative consequences, 66 per cent of teen girls who posted suggestive content said it they did it to be "sexy or flirtatious."

While 52 per cent said they did it as a "sexy present" for their boyfriends, 40 per cent said they did it as a joke, the survey found.

About 15 per cent of teenagers who have sent sexually suggestive content such as text messages, email, photographs or video say they have done so with someone they only know online.

Some 18 per cent of teenage boys also said they sent or posted nude or semi-nude images of themselves, the survey said.

"That so many young people say technology is encouraging an even more casual, hook-up culture is reason for concern, given the high rates of teen and unplanned pregnancy in the United States," said Marisa Nightingale of the National Campaign to Prevent Teen and Unplanned Pregnancy.

"Parents should understand that their own notions of what's public, what's private and what's appropriate may differ greatly from how teens and young adults define these concepts." (dpa)