The police are frequently failing to record rapes and sexual offences as crimes, a damning report by the national policing inspectorate has found.
Her Majesty's Inspectorate of Constabulary (HMIC) expressed "very considerable concern" that rapes and other sexual offences against vulnerable people were being dismissed by officers.
The interim report "Crime recording: A matter of fact" found that "inadequate or absent training" of officers in England and Wales, meant that many victims had been abandoned by the police.
Their audit turned up 14 sexual offences including 11 rapes that had been falsely classified as non-crimes by officers.
In one case, a 13-year-old boy with autism had reported a sexual assault by his older friend, only for officers to wrongly write off the case as a "sexual experimentation".
In another case, a woman reported a rape to her doctor after a man had refused to stop having sex with her after she told him she was in pain. Officers wrongly concluded that no crime had occurred.
The inspectorate found that up to one-in-five of all crimes were being wrongly classed as non-crimes, meaning that crime levels across England and Wales could be dramatically higher than assumed.
This finding confirm the claims of police whistleblower PC James Patrick who had claimed that crime was being under-recorded by as much as 20%.
HMIC say they cannot rule out that the under-recording could be down to "discreditable or unethical behaviour," by officers.
However, they also blame poor training, inadequate supervision and an excessive workload placed on officers, for the problem.
The report follows another report by the public administration select committee (PASC), which found that the public "can't rely on Police Recorded Crime Statistics".
Committee chair Bernard Jenkin said HMIC's new report was "devastating."
"HMIC's interim report on the inspection of crime data integrity in police forces in England and Wales is devastating," he said.
"It corroborates the main findings of the PASC report. Like PASC, HMIC is 'seriously concerned' about 'weak or absent management and supervision of crime recording, significant under-recording of crime, and serious sexual offences not being recorded'. They are finding cases when the police have failed to prosecute offences when they should have done. This both under-records crime and over states clear-up rates."
The officer who first blew the whistle on the police's manipulation of crime figures has now been accused of "gross misconduct" by the Metropolitan Police, for appearing on TV and radio "without permission."
"A reasonable person might well ask questions about the motivation of this new action," Patrick wrote in a blog post on his personal website.
"Another reasonable person might simply see it as vindictive."
Patrick has resigned from the force and is due to leave later this month.