A charity which protects young people in Burton and South Derbyshire has called for action to stamp out online sex abuse after figures show a third of teenage UK girls have suffered internet harassment.

Sandra McNair, the NSPCC head of service for Staffordshire and Derbyshire, said modern sex education was needed to prevent teenagers - particularly young girls - from falling victim to sex pests.

The call follows research by charity Childnet which found 31 per cent of girls aged 13 to 17 had been targeted with unwanted sexual attention over the Internet, compared with 11 per cent of boys.

One in 10 young people reported receiving threats of sexual violence, including rape, the survey of 1,559 teenagers found, while 31 per cent have witnessed it happen.

So-called revenge porn was also shown to be prevalent among children, with 51 per cent of those surveyed, aged between 13 and 17, having seen it circulated.

Revenge porn was recently outlawed by the Government and is defined as the sharing of private, often sexual or explicit material, photos or videos, of another person without their consent.

Meanwhile, nearly a quarter of teenagers know of someone secretly taking sexual images of another person and sharing it online, known as "upskirting", according to the research.

Mrs McNair said: "The level of online sexual harassment being experienced by girls in particular is extremely worrying. Childline often hears from young people who have been pressured into sending sexual images of themselves and then quickly regretting what they have done.

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"To help prevent sexual harassment we need sex and relationship education that fits with the modern world and teaches children about recognising abuse online, including grooming and sexting."

The Childnet report, released as the Government prepares new guidance on sexual harassment in schools, examines sexual harassment in four categories, non-consensual sharing of explicit material, threats and coercion, sexualised bullying and unwanted sexualisation.

Will Gardner, chief executive of Childnet, said: "Digital technology plays a central role in young people's lives but it has opened the door for a range of new forms of sexual harassment, making societal discussions about these issues more pertinent than ever.

"It is evidently something that as a society we can no longer ignore.

"Throughout the development of this report we have listened to stories of young people who are navigating the complexities of relationships in a digital age and in some cases are facing the worst forms of peer-to-peer victimisation and online sexual harassment."

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Among the other findings made by the report was that more than a quarter of UK teenagers had been the victim of online rumours about their sexual behaviour and 12 per cent of teenagers claimed they had been pressured by their partner into sharing nude images.

Fake profiles have become a common way for offenders to circulate sexual material, the study found.

Mr Gardner added: "We believe that all young people have a right to be safe and free to express themselves in digital spaces.

"This report underlines how essential it is that we all work together to ensure that online sexual harassment is not an inevitable part of growing up."

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If a young person is worried about an image they can speak to a trusted adult or contact Childline on 0800 1111 or at Childline.org.uk who can take steps to get the image removed.