A teenager was raped by a gang of men after being lured to a secluded nature spot, police said.
The 17-year-old had met the group earlier in the day and walked with one of them into a woods near the Jubilee River in Slough, according to Thames Valley Police.
Four other men who were part of the earlier group then arrived at the location in a small silver car. They are described as Asian.
The girl was then raped by "several of the men," police said.
Det Insp Nicola Hurdley said: "We are still speaking with the girl at this time to get a full picture of what has happened, but what we do know is that while she was in this wooded area she has been raped by several of the men."
Rape cases that are dropped by the police would be reviewed under Labour plans to boost the rights of victims, Yvette Cooper will say.
The shadow home secretary will pledge to give victims a "strong voice" and warn the low rate of allegations being pursued is "shameful".
In a speech to the Fabian Society, she will insist Labour is focusing on reforms that give more power to individuals and communities but stand ready to make tough decisions about making savings.
"Just as in the criminal justice system, across our public services, ministers are driving fragmentation, reorganisation and competition just at a time when local services need to collaborate more to deliver better services and save money too", she is expected to say.
Judges should warn juries about "myths and stereotypes" associated with rape at the start of trials, two senior legal figures have said.
Misconceptions, such as if a victim was drunk, or had previously consensual relations with the perpetrator can lead to juries deciding rape has not occurred, Alison Saunders, the Director of Public Prosecutions, and Martin Hewitt, of the Association of Chief Police Officers, told The Independent.
Ms Saunders called on juries to hear directions on myths and stereotypes about rape at the start of the trial, rather than at the end when the judge is summing up the case.
"All of us are human - you're going to hear the evidence, you're going to make a judgment and then you're told to set your judgment aside and (are told by the judge) these are the things you should be taking into account - actually it's better to hear that at the beginning," she said.
Mr Hewitt added: “I think we need to focus on the trial process. There is some really good practice, but I still think there are too many examples where the trial process is very negative for the victim.
The two experts are heading a task force to investigate the fall in numbers of successful rape prosecutions and what can be done to reverse the trend.
Charity Rape Crisis England said that releasing data on rape cases reflected a commitment to transparency and scrutiny of police practice.
Spokeswoman Katie Russell said: "Nonetheless, Rape Crisis is still extremely concerned by the persistently high levels of 'no-criming' today's data reveals, as well as by the huge disparities in statistics between different police forces."
This leaves us wondering how many more reports it will take before we see a real and marked improvement in criminal justice for rape survivors.
– Charity Rape Crisis England spokeswoman Katie Russell
She said that the figures show that little has changed since a 2012 report from Her Majesty's Inspectorate of Constabulary (HMIC), which highlighted concerns around inconsistent and inadequate recording and investigating of sexual offences.
Lincolnshire Police had the highest "no-criming" rate for adult rapes - that is, an offence initially recorded as rape, but then declassified - at 33%, compared with Cumbria, which had the lowest no-criming rate at 3%. The average no-criming rate is 12%.
: "The wide disparities between different areas' reporting, detection and 'no crime' rates may indicate that the culture of scepticism remains in some police forces.
"This is not a surprise to us. Our member organisations know how deep disbelief and victim-blaming goes in institutions and communities.
"But the police play a critical role enabling rape survivors to access justice, so these disparities and attitudes must be urgently tackled."
– Professor Liz Kelly, chair of the End Violence Against Women coalition.
Rape charities and women's rights groups said data, which was pulled together for the first time by the cross-Government, multi-agency Rape Monitoring Group (RMG), revealed disparities and attitudes which must be "urgently tackled".
A postcode lottery in the way rape cases are handled by police has been highlighted by figures showing wide variations between forces across England and Wales, it is claimed.
Differences in the rate of recorded rapes, charges or cautions for the offence and records later declassified as a "no-crime" incident have raised fears of a "culture of disbelief" among some of the 43 forces covered by the data.
Among key contrasts, Northamptonshire Police had the highest rate of recorded rape at 34.8 per 100,000 adults in the year to March 2013, while Durham Police had the lowest at 9.8 per 100,000 adults. The average is 22 rapes recorded per 100,000 adults.
There were some measures already in place, he explained: "We put training in place to make sure that everyone who potentially comes into contact with that person has the knowledge to put them to the specialist."