Young people aged between 15 and 24 are the group most affected by sexually transmitted infections (STIs) in the UK, according to recent research published by the Health Protection Agency. Women are particularly at risk, the figures showed.

Last year there were 482,696 new STI diagnoses - almost 12,000 more cases than in 2008.

In this week's Guardian Focus podcast Rosie Swash explores the reasons for this. She speaks to experts at sexual health charity Brook, Chris Bryant MP and teenagers themselves to find out why the numbers are so high and what needs to be done to get them down.

The lack of adequate sex education at school is often blamed, and Rosie visits her old school in north London to find out how they deal with this.

Many argue that parents exert a stronger influence over young people than schools. Young people tell Rosie about their experiences in broaching the subject with their mothers and fathers.

She explores the cultural reasons for the high numbers of STI's. Do we have double standards when dealing with sexually active girls?

Listen to the podcast to find out how Rosie got on - and leave your comments below.