Agony aunts such as Clare Rayner and Deirdre Sanders could face prosecution under the Government's Sexual Offences Bill as well as newsagents that sell teenage magazines to children.
Politicians are concerned that clauses in the Bill, which is going through Parliament, could even catch out family-planning advisers who publish material for children about sex education.
Health advisers who hand out condoms to under-16s and biology and sex education teachers could also be affected by the Bill, which will make it a punishable offence to communicate "with a child, where any part of the communication is sexual". Opposition MPs are afraid that a clause making an offence of "giving a child anything that relates to sexual activity or contains a reference to such activity" could have unforeseen victims.
Nick Mazur, the deputy chief executive of the Periodical Publishers Association, the industry association for magazines in the UK, said: "We are extremely concerned if the Sexual Offences Bill restricts the access of young people to bona fide advice and information on sexual issues.
"Teenage magazines, and their problem pages, are often the only source which young people can turn to for this advice. Agony aunts or teen magazine columnists who address these emotional aspects of sex are now at risk of committing an offence under Clause 15, such as 'encouraging a child to take part in sexual activity'."
A cross-party group of peers is planning to amend the Bill when it comes back to the House of Lords next month, to stop innocent people being subjected to sexual offence orders. Failure to abide by the orders, which could prevent distribution of the material, is punishable by prison.
The campaign to change the wording of the law is being led by Baroness Walmsley, the Liberal Democrat frontbench peer and a former biology teacher.
"It's very important that we have high quality sex education and it's vital that we don't legislate in any way to get in the way of bona fide people delivering advice, including agony aunts," she said. "It is difficult enough to get people to do these jobs without the danger of prosecution. The law has to be clarified." Childline, the children's advice line where sexual matters are often discussed in confidence, is also concerned that it could find itself inadvertently on the wrong side of the law. Also, youth workers who hand out condoms at nightclubs to promote safe sex could be at risk.
Ministers have admitted that the wording of the Bill could catch out people innocently discussing sex with children, although they say police would not pursue them because they are not harming the child.
Lord Falconer of Thoroton, a Home Office minister, said Lady Walmsely was right. "The requirement could in theory catch the sex education teacher or a biology teacher at a school showing children diagrams or models of reproduction," he added.
The Home Office said last night that the sexual offence orders would not be imposed on people who did not intend to harm children and that it did not intend to change the law. But the Family Planning Association (FPA) and the Periodical Publishers Association said there "was no room for any ambiguity" and safeguards must be added to the Bill
An FPA spokesman said: "We produce printed material which is used in schools about how young people develop physically, contraception and sexual infections. The problem is that the law is ambiguous and you never know how it could be interpreted once it goes through."