The La Trobe University study shows more than 70 per cent of sexually active year 10 to 12 students have sent explicit text messages, 84 per cent have received them, and more than half have sent naked or semi-nude photos or videos of themselves.

But despite fears the increasing use of technology is encouraging promiscuity and sex from an early age, the report reveals that the rate of intercourse is actually dropping as more teenagers choose to wait.

Conducted every four to five years and considered the most accurate snapshot of youth sexual behaviour, the fifth National Survey of Australian Secondary Students and Sexual Health found 23 per cent of year 10 students and 50 per cent of year 12s have had sex, compared with 27 per cent and 56 per cent respectively in the 2008 poll.

Almost 70 per cent cent are sexually active in some way – having experienced oral sex, deep kissing or genital touching – down from 78 per cent in the last survey.

Released exclusively to The Sunday Age ahead of today’s launch in Melbourne, the 2013 survey – involving more than 2100 students from 436 government, Catholic and independent schools across Australia – for the first time looked at the way teenagers are interacting sexually online.

Commissioned by the federal department of health and used to inform sexual health policy, it shows almost 90 per cent of 16- to 18-year-olds use social media such as Facebook, Twitter or Instagram every day, with one in five saying they use the sites for sexual purposes.

More than half (54 per cent) of all those surveyed have received sexually explicit written text messages, 42 per cent have received explicit, nude or nearly nude photos or videos, and a quarter have sent such images or videos. Among sexually active students, more than two-thirds are engaging in sexting.

Lead author, Professor Anne Mitchell, who has conducted the study since 1992, urged caution saying that, despite fears a sexualised, digital culture was increasing pressure on young people to have sex before they were ready, the proportion having an experience of unwanted sex in 2013 – due to pressure from partners, friends or being frightened or drunk – had fallen from 32 per cent in 2008 to 25 per cent.

"Despite the advent of this technology, sexual activity has remained fairly stable over the past two decades. It’s a social, online world kids live in and sending these images and messages is part of their sexual relationships so it’s really a new form of courtship," said Professor Mitchell from the Australian Research Centre in Sexual Health and Society, at La Trobe. "It appears to be happening universally and, while we need to be aware of the harm that can come if those messages are sent out far and wide or misused, it doesn’t appear to be doing harm for the majority of kids. Parents need to stop panicking about the use of technology and trust their kids – talk to them about their relationships, treating others well, having the kind of sex they want and being safe."

More than 70 per cent of those surveyed said they had no regrets after having sex, while 54 per cent of those who were not sexually active were "proud to say no", and half wanted to be in love before losing their virginity.

The proportion of teenagers having had three or more sexual partners fell from 30 per cent in 2008 to 23 per cent in 2013, while 55 per cent of those having sex were doing so in a relationship.

And while 17 per cent of young people were drunk the last time they had sex, overall, 40 per cent had never drunk alcohol – up from 21 per cent in the 2008 survey

Erin Filan,18, finished year 12 at a Catholic girls school in Northern Sydney last year, and is a member of the Youth Brains Trust at Young and Well Cooperative Research Centre – a not-for-profit group exploring the role of technology in young people’s lives. She says older generations often misunderstand the way teenagers interact online and argues sexting is just another form of sexual expression.

"It adds another level to the good old four bases – people don’t feel they only have one option if they want to get intimate with someone but they don’t have to risk pregnancy or STDs. If you don’t want to have sex but you still want to be sexual you can get that energy out in a safe way,’’ she said. ‘‘Even if these images do get out – if someone saved a snapchat or something like that – people know to not put identifying features in it."

Matthew Church, an 18-year-old from Melbourne, and also a Brains Trust member, said sexting was "intimacy on-the-go" for a mobilised generation.

"Relationships these days are starting from the top and working down. Courtship happens very physically and then becomes emotionally intimate later on in the process. But all of the young people that I’m friends with and I talk to definitely say their transition into sex happens when they’re ready and on their terms. Young people are more clued in than we’re given credit for. We know how to use technology in a safe and informed way."