A bid to force doctors offering abortion or contraception advice to under-16s to inform the child's parents has been rejected by MPs.
Angela Watkinson said parents should be helped to protect children
Tory MP Angela Watkinson argued that current sex education encouraged girls to have sex before they were ready.
But MPs voted by 159 to 87 to retain the current guidelines guaranteeing confidential advice to under-16s.
For the Lib Dems, Dr Evan Harris argued that child protection and patient confidence had to be retained.
About 4,000 under-16s a year have abortions in England and Wales.
Mrs Watkinson said current policy was not working as the rate of abortions, pregnancies and sexually transmitted disease among young teenagers was "shamefully high".
Presenting her Contraception and Abortion (Parental Information) Bill to the Commons on Wednesday, she said the "plethora of information" on contraception gave encouragement and false assurances to young girls.
"All the indications are that many children are becoming sexually active well before they are either emotionally or physically mature," she said.
She said the free provision of the morning after pill had not reduced teenage pregnancies, of which there were 7,464 in 2005 - some mothers as young as 13.
"It's time to try a different approach."
Mrs Watkinson argued that parents could help their children to resist peer pressure and to delay their first sexual experience until they are older - reducing the risk of pregnancy or sexually transmitted infections like chlamydia.
She also said that some parents, having found out that their daughter had had an abortion, might have helped her to bring up the child.
"The provision of lots of sex information has not worked. Sex information should be replaced with sex education," she said.
"In education about the real risks involved and the likely outcomes, the advice to underage girls should be to abstain, to wait, to delay, to resist. Not to use contraception and believe they will not come to any harm. Parents need to be part of this process."
But for the Lib Dems, Evan Harris, a medical doctor and member of the BMA's medical ethics committee, argued against the change.
He said current guidelines on abortion and contraception already required doctors to consider whether youngsters understood the potential risks of treatment and encourage youngsters to inform parents of the consultation
"It is important for persons under 16 seeking contraception advice to be aware that although the doctor is obliged to discuss the value of parental support the doctor will however respect their confidentiality if necessary," he said.
The "best interests of the patient" must govern the doctor's behaviour, not "ideology", he said.
He said it was rare for youngsters not to inform their parents or another adult, adding: "It is on those rare occasions we have to have concern.. we have to have regard to the safety of individual patients."
Mrs Watkinson's bid was supported by Professor David Paton, of Nottingham University Business School, who said fears that involving parents would mean girls were put off seeking help were not backed up by the statistics.
But Anne Weyman, chief executive of the FPA (formerly the Family Planning Association) said it would deter young people from seeking essential advice.