The scale of the problem and victims' psychological effects is hugely under-estimated, according to the report's author. No national figures have been collected in the UK, but small surveys have found that from 50 to 60 per cent of women have been exposed to. One estimate is that 40 million women a year are victims of flashing in the United States.
Rosalind Beck, of the University of Wales, College of Cardiff, said in her draft report Rape From Afar: Men Exposing to Women and Children, many victims feel their experiences have been trivialised. Many, including the police, joked about the crime, which some women compare to being sexually assaulted.
Twenty-five victims, aged from 23 to 57, including four men, were interviewed in the study. The ages at which they had been exposed to ranged from five to 55. The women had been flashed at on 68 occasions, some had been exposed to as many as eight times. The men had experienced eight incidents. Flashers were aged between early teens and early nineties, and few fulfilled the "dirty old man in a raincoat" stereotype.
Some of the findings were presented at last week's British Criminology Conference at Loughborough University. During the discussion, a conference- goer recalled that a student at Cambridge University masturbated on his meal in front of a female student during a football dinner.
Only one-quarter of the women victims reported the flashers to the police. One response from the police was to say: "Don't worry, they are harmless." None of the men contacted the police.
Among the incidents they encountered were men exposing themselves in public toilets. Ms Beck said it was easy to find male victims - some of whom expressed fear at being flashed at - and concluded it was, therefore, a fairly common occurance.
Of the two reported cases of women "flashing" at men, in one a woman bared her breasts at a residential home and the other was a full frontal exposure while the male victim was on holiday. There was one case of a woman exposing herself to another woman.
The women victims believed the flashers exposed themselves for a variety of reasons, including an attempt to humiliate, gain power, frighten, threaten and get attention. Few believed mental illness was the cause.
The study concludes: "The women in this study have shown how being a victim of this form of sexual attack can have a significant impact on their lives and can be interpreted by them as a message from the man that, if he chose to, he could also rape or murder them.
"Facts about exposing are hidden behind a mythology of the stereotypical harmless 'flasher' who will do 'nothing else' to the victim, and who provides a suitable topic for jokes. This is compounded by an unhelpful police response to the victims.
"Women's reality of this form of sexual violence is very different from the public image."
'I thought he did it because
of the way I looked at him'
Among cases highlighted in the study was that of a woman, aged 27, who was exposed to when she was 10. A man took his penis out while the girl was cycling with her cousin on a country lane. He grabbed her cousin and she ran for help.
She said: "I blame myself because I thought he did it because of the way I was looking at him. Only in the past few years have I been able to talk about it. I can still see it so clearly and vividly. It messed me up. I don't have eye contact with men on the street now. I think they are less likely to attack me."
In another case a woman was on the lavatory in a pub when the door, which did not have a lock, was opened by a man who masturbated in front of her. The woman now refuses to use pub lavatories on her own.
In a third incident a 34-year-old woman saw a man masturbate at a window in front of her. She said: "I was totally chilled, I went cold. I got a feeling in the pit of my stomach, like when I found out I was pregnant, like witnessing a car crash."
Other women in the study said they had regularly been exposed to on public transport, such as London Underground trains, but other passengers often considered it a "joke". On one occasion a man exposed himself to a woman while sitting in a car with his friend.