The number of scenes on US TV featuring sex has nearly doubled in the last seven years, a study has suggested.
Gilmore Girls starring Alexis Bledel was one of the shows cited
The survey for US health pressure group the Kaiser Family Foundation showed there were 3,783 scenes in a 1,000-hour sample, compared with 1,930 in 1998.
It found that 70% of shows had sexual content, ranging from a reference to full depiction, with five sex-related scenes per hour on average.
TV bosses said parents have technology to bar content they deem inappropriate.
The foundation's survey found the number of sex-related scenes in the leading teen TV shows was nearly seven per hour.
It cited examples including a discussion of sex on the WB's Gilmore Girls to a depiction of sexual intercourse in Fox's The OC.
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The study examined programmes on ABC, CBS, NBC, Fox, WB, PBS, Lifetime, TNT, USA Network and HBO.
Lead researcher Dale Kunkel said it was generally accepted that TV influenced children's behaviour.
"Their sexual knowledge, attitudes and behaviours are all shaped in part by the characters in stories that television conveys," he said.
Tony Vinciquerra, president and chief executive of Fox Networks Group, said parents had controls such as the V-chip, which is built into TV sets to allow parents to block shows based on ratings.
He added that TV bosses were aware of parents' concerns.
"We have debates every minute of every day about what goes on television," he said.
The Kaiser study suggested a slight rise in shows promoting a message about contraception and the risks in having sex.
Among the shows that featured sexual content, 14% had discussions about waiting to have sex or safe sex, up from nine per cent in 1998.
The report follows a review in April by the Parents Television Council, which claimed that many US shows did not have enough prior warnings on sex and violence.