Parents feel a need to talk to their teenage children about sex and relationships - but are unsure how to go about it, surveys suggest.
Young relationships can prove awkward for all concerned
The charity Parentline Plus said two thirds of its calls about sex and relationships were from parents worried about daughters getting pregnant.
More than half of the calls (56%) concerned 13-15 year olds.
Another survey suggests 83% of teenagers found parents embarrassed or unhelpful when giving advice.
Parentline Plus - which runs a free helpline - said many of the calls it had taken about children's sexual behaviour and relationships were from parents also worried about a range of other things.
These included mixing with a bad crowd, lying, smoking, drinking and substance misuse.
Thirteen per cent of calls were from parents whose children had been threatening to leave home.
It also heard from parents worried that their underage daughters were having sex with older men, and from parents unsure about what was "normal behaviour" for teenagers.
"Many parents feel desperate and isolated by their children's behaviour and in many cases don't know where to turn to for advice and support," the charity said.
"Evidence suggests that when teenagers talk to their parents about sex, they are more likely to delay sexual activity, have fewer partners and use contraception."
It said there was a need for more co-location of health, police, social services and voluntary organisations to make them more accessible to families.
The other survey, commissioned by Sense Interactive CDs, suggests parents may often feel ill-equipped to offer advice.
Almost a third said their own sex and relationship education had been "non-existent".
"A staggering 83% of teenagers found that their parents were embarrassed or unhelpful when it came to advice about sex and relationships."
Two thirds of fathers suggested school was the best place for their children to find out about sex and 42% of parents thought family doctors would be best.
"A shocking 86% of young people said that they feel pressurised to have sex, with 40% feeling that drugs and alcohol lead to an even greater pressure to have sex."
But three quarters of the parents surveyed thought their children already received sufficient education about sex and relationships at school.
The organisation is promoting a new CD-ROM for youngsters, which it has developed with the assistance of the National Children's Bureau.
The bureau's assistant director of children's development, Simon Blake, said: "We hope that this CD will help young people to realise that they are not alone in being anxious or ignorant about sex and relationships - and that feeling under pressure is not a good reason to start having sex."
There is also an advice booklet for parents and teachers.