The government is to give teenagers the facts about sex that they fail to get from either their parents or school in a major campaign aimed at cutting the number of pregnancies among teenage girls.

Ministers are determined that the campaign will not be judgmental. Research commissioned by the Department of Health and the Central Office of Information, which will be published later this month, states categorically that teenagers "strongly reject communication they perceive as patronising, authoritarian or not addressed to them as equals. This includes sources which they perceive to be treating them as children, that try to be like them (captured in the phrase 'trendy vicar') or that tell them what to do or to believe."

Messages that are factual and non-judgmental have some effect, say the researchers, "whereas messages based on fear and on abstinence ('just say no') have clearly proved ineffective."

The campaign is still in the planning stage and ministers are reluctant to be drawn on the detail because of the inevitable controversy. The churches, many parents and rightwing morality groups will be outraged that young people will not be given a clear message that under-age sex is wrong and that sex within marriage is the ideal.

Yvette Cooper, the minister for public health, said many things were yet to be decided, but certain principles were clear. "Getting teenage pregnancies down means working with teenagers and parents to see what works. The research shows that teenagers take no notice of patronising messages and we're very clear that the campaign must be as much about boys as about girls."

The government has earmarked £15m for its publicity campaign - half of which it intends to come from the private sector. Radical measures are thought necessary because the UK has the highest teenage pregnancy rate in Europe , with about 90,000 conceptions a year.

The advertising agency Delaney, Lund, Knox, Warren has been given a contract to begin exploring with teenagers the style and content of messages they will accept. Another arm of the campaign will focus on encouraging parents to talk to their children.

The government's research, compiled by independent researcher Christine Eborall from studies in the UK and abroad, has clearly shown that teenagers most want to hear it from mum and dad.

Where parents talk to their children about sex, the children are more likely to delay and use contraception but, says the government's research, "nowadays most parents feel ill-equipped to fulfil this role. They find the subject embarrassing and are uncertain about what to say or when and how to say it. They feel they ought to give a formal sex talk, but the worry that their children probably already know more than they do inhibits them from initiating any communication.

"Fathers are particularly poor in this respect, with the result that boys often miss out completely on sex education in the home. And the fact that sex education is taught in school gives parents an excuse to avoid the issue."

But school sex lessons, where they exist, are embarrassing and teenagers are left "ignorant and desperate for more information". It is not surprising many girls turn to teen magazines. "However, they [the magazines] are also perceived by parents and older young people to encourage sex and to foster dissatisfaction and frustration among young readers by setting unachievable standards of beauty and sexual attractiveness."

Young people quickly learn that sex is taboo and inherit their elders' stereotypical views - boys want to be macho studs while girls unrealisticly associate sex with romance. This social climate, together with much greater exposure to the adult world through families and the media than before, ignorance about contraception and diseases and the use of alcohol, are all factors in early and unprotected sex, the research says.

Ministers are being urged to build the campaign around a single central idea based on love and sexual attraction, which would interest teenagers and become familiar through a slogan or jingle. Also being considered are the use of humour, animation, cartoons and the internet.