It's easy to become complacent. It's easy to read headlines that show an MP's suggestions are not being taken up by parliament and presume that we don't need to take them seriously. When an amendment to a health bill demanding that women be given pre-abortion counselling that could be provided by religious, pro-life groups gets voted down, surely we can breathe out, relax a little and reassure ourselves that the threat to women's reproductive rights is over?

Far from it. Now – when there's a reasonable lull in rightwing press coverage of the subject – is precisely when we should be concerned about the more reactionary quarters of parliament. Because when they're not openly deriding sex as something that corrupts the minds of the young, women or society, you can be sure that behind the scenes they're planning new ways to undermine the rights that we have taken for granted for generations in this country.

This is no exaggeration: MP Nadine Dorries may have lost the vote, but another bill she put forward earlier this year, which demanded girls should be taught abstinence as a compulsory part of sex education, is due a second reading in parliament early next year.

This proposed bill was, Dorries suggested, not only a way to counter the apparently high rate of teenage pregnancy but also to stop sexual abuse. "If a stronger 'just say no' message was given to children in school," Dorries argued, "there might be an impact on sex abuse, because a lot of girls, when sex abuse takes place, don't realise until later that was a wrong thing to do …" So if girls only knew how to say no to sex, that would somehow prevent their being sexually abused? And what about boys? Or do they not count?

In addition Dorries is basing her bill on the premise that teaching abstinence stops teenagers becoming pregnant. In the US, where abstinence-only health programmes blossomed in pre-Obama years, the rate of teen pregnancy is still the highest in the developed world. In contrast, a thorough sex education, based on scientific evidence and a lack of moralising, has a proven positive effect in this area: teen pregnancy rates in the UK are at their lowest since the early 1980s – not that you'd know it in some corners of the press.

The fact that an MP who can spread such inaccuracies is proposing a nonsensical, victim-blaming bill should give us all cause for concern. Dorries has had a pretty good reign in the media recently: as an outspoken MP she has the opportunity to make unsubstantiated claims such as her anecdote – often repeated by newspapers – that seven-year-old girls are being shown how to put a condom on a banana in sex education classes. Moral outrage followed, but did anyone demand evidence to support such a lurid claim – and was Dorries ever able to provide proof that such a situation occurred? Teachers and those who work with young people in sex education are aware of her scaremongering but have no voice to challenge it.

No longer. This isn't a time to stay silent. When Dorries can spread misinformed opinion as fact, and the government can – completely unchallenged by MPs – replace the British Pregnancy Advisory Service on a new sexual health advisory panel with Life, a religious, anti-abortion group, it is time to counter what is fast becoming an anti-sex, fundamentalist mandate.

I'm running an event called Sex Appeal on behalf of Brook, the young people's sexual health charity, to get people to speak out and to openly challenge those who spread misinformation about sex, sexuality and sex education.

If we don't fight against the encroaching attacks on access to abortion we will see a further erosion of women's reproductive rights. And if we don't fight on behalf of young people and the education they have a right to then the impact on their lives, their relationships and their sexual health will be felt for generations to come. Nadine Dorries, we're ready for you.