The NSPCC has said that there were 8,077 children who were accused of sexual offences - 3,868 in 2012/13 and 4,209 a year later. Crimes included serious sexual assaults, rape and obscene publication offences. NSPCC chief executive Peter Wanless described the results as "deeply concerning".
Most victims knew their alleged abuser, with some of the most common crimes being teenage boys abusing female acquaintances, according to the NSPCC. It said most abusers were male though there was a small proportion of female abusers, and victims were male and female.
"We know that for many older children pornography is now part of life. Easy access to hardcore, degrading and often violent videos on the internet is warping young people's views of what is normal or acceptable behaviour.
Figures obtained by the NSPCC show more than 8,000 under-18s were accused of sexual offences against other children in the last two years.
The children's charity contacted 42 police forces across England and Wales with a Freedom of Information request asking for the number of under-18s who had been accused, the youngest victim and the youngest accused. Of the police forces contacted, four did not respond.
The youngest child to be accused was aged just six, while the youngest victim had not yet reached their first birthday.
Rolf Harris hid behind his "happy-go-lucky persona" while committing a string of sexual offences which damaged the lives of his victims, a children's charity has said.
The NSPCC received 28 calls about the veteran entertainer through its helpline, including 13 people who said they had been abused by him.
Speaking after the guilty verdict, Peter Watt, director of national services at the NSPCC, said:
We’re delighted to have played a major role in helping bring Rolf Harris to justice and to uncover the dark side of an entertainer who hid behind his happy-go-lucky persona while committing sexual offences.
His reckless and brazen sexual offending, sometimes in public places, bizarrely within sight of people he knew, speaks volumes about just how untouchable he thought he was.
Like many children overwhelmed by the trauma of sexual abuse, those he targeted struggled to understand the ordeal they had been through at the time, and battled to come to terms with the impact of their experience at his hands. Some felt ashamed at what had been done to them.
But now the world knows only one person should be ashamed, and that is Rolf Harris.
Parliament must "recognise extreme emotional abuse" and give child protection services greater power by legislating against it, a senior member of the NSPCC said.
John Cameron, head of child protection operations, said the so-called "cinderella law" was not about punishing parents who did not buy their children "the latest gadgets or trainers":
The Government has indicated they are set to outlaw extreme emotional cruelty and this is a positive step forward and the publicity around this and highly publicised cases such as Daniel Pelka may have contributed to the sharp increase in calls.
We must recognise extreme emotional abuse for what it is - a crime - and those who carry it out should be prosecuted.
This isn't about prosecuting parents who don't buy their children the latest gadgets or trainers, this is about parents who consistently deny their children love and affection.
Peter Watt, the NSPCC's director of national services, said:
The responses these victims received when they first revealed Savile's sickening crimes makes heart-rending reading.
They were ignored, dismissed, not believed, laughed at and, astonishingly, told in some cases they should feel lucky he had paid them attention.
Half a century on, the world finally discovered just how dreadful his crimes were - something these men and women had known all that time but felt powerless to do anything about.
The anger, frustration and sheer helplessness of the situation obviously damaged their lives in various ways.
But they showed true courage in coming forward once more to talk about their experiences and hopefully they can now start to put the terrible trauma behind them.
According to the report, Would They Actually Have Believed Me?, some of the victims, who were aged between eight and 26 when Savile assaulted them, told hospital staff, who dismissed their claims.
One of the 26 victims interviewed by NSPCC counsellors went to the police but no action was taken. The vast majority were children when they were abused but four were adults.
The NSPCC said the research, which was commissioned by Her Majesty's Inspectorate of Constabulary, highlighted the "devastating scars" that victims had suffered from the abuse, with some turning to drink and drugs to cope.
Others have suffered mental illness, poor relationships or contemplated suicide, it said.
Head of Child Protection Operations at the NSPCC, John Cameron, says children have a "greater likelihood" to be involved in criminal and anti-social behaviour if "they have been in receipt of smacking as a standard form of parenting".
Speaking with ITV News, Mr Cameron said smacking does not have a positive, long-term impact on children.
"This is not about prosecuting, persecuting and criminalising parents, but it's about giving a very strong message in our society that children should have the same rights as adults in law to be protected from physical assaults," he said.
The NSPCC has welcomed Google and Microsoft's decision to block images of child abuse via their search engines, but emphasised, "We must keep one step ahead."
Peter Wanless, chief executive of the children's charity, said:
Each image is a crime scene where unspeakable abuse was committed.
As sex offenders get ever more technologically advanced in pushing their vile trade, we must keep one step ahead and this requires a concerted and sustained effort from all quarters.
This is the key child protection issue of a generation - we cannot fail.
The NSPCC is calling for social media sites to do more to make their online platforms safer for the millions of children who use them by bypassing the age restrictions. Claire Lilley, NSPCC's head of child safety, said the risks to 11 and 12-year-olds need to be evaluated by the companies.
There is a significant jump in the numbers of children who have a social networking profile at age 11 - which coincides with the move to secondary school for most UK children
We estimate that around half of the UK's 11 and 12-year-olds have a profile on a social networking site with a minimum age of 13.
Age verification is a nut that social networking sites are yet to crack.
We want social networking sites like Facebook and Twitter to take a pragmatic approach - if younger children are determined to use social networking sites for over 13 year-olds, the sites can't simply turn a blind eye.
BeatBullying has backed calls from the NSPCC for social media sites to do more to protect their young users.
BeatBullying founder Emma-Jane Cross said:
"This research underlines the urgent need for social networking sites to take their young users' safety much more seriously.
"We believe in the right of children to go online without fear of being bullied or harassed, and this cannot be achieved until social networks put adequate resources behind safeguarding and user verification policies."