Campaigners have called for urgent changes to the law to make "upskirting" criminalised alongside other sexual offences, as the first official figures on the craze show complainants as young as 10.
Victims, politicians and equality groups have urged the Government to provide "an effective criminal law" for upskirting, which often sees perpetrators escape punishment for taking photographs or videos of a victim's groin area from beneath their clothing.
There is currently no law banning upskirting, with victims left to pursue voyeurism or indecency claims in a handful of cases.
Campaigners say the situation echoes that of image-based sexual abuse - often referred to as revenge porn - which lingered in a legal grey area until a law was introduced in April 2015 following a national campaign.
It comes as the first official figures on the prevalence of upskirting, revealed by the Press Association under freedom of information (FOI) laws, shine a light on the issues facing police dealing with reports from victims.
Just 15 of 44 police forces contacted had record of any allegations of upskirting in the two years since revenge porn was made illegal, while 14 said there were no records. A further 15 forces either refused or failed to respond.
Those with data showed 78 incidents reported in two years, with 11 resulting in suspects being charged.
Campaigners said the true number is likely to be much higher, given the difficulties with police being able to log and investigate in many cases.
There was insufficient evidence to proceed in several cases, including on an alleged sexual offence on a 10-year-old girl in 2015, Avon and Somerset Police said. Locations included public spaces such as nightclubs and restaurants.
Clare McGlynn, professor of law at Durham University and an expert on sexual violence, said the FOI data showed there "are few public places where women are free from this abuse".
She said: "The Government's continuing failure to provide an effective criminal law against upskirting breaches women's human rights.
"We are entitled to protection from degrading and abusive treatment, whether offline or online - and we are entitled to have our privacy in public respected.
"We are also entitled to a law that is fit for purpose, a law that treats this abuse as a form of sexual offence and that provides anonymity to all complainants. Only then will victims feel more willing to come forward and report to the police and support prosecutions."
MP Maria Miller, who chairs the women and equalities select committee, said it was "concerning" if the police felt the law did not give them adequate powers to stop the "horrific crime of upskirting".
She said: "Attempting to take a photograph underneath a skirt is a gross violation of privacy and potentially an act of indecency.
"However, as I know from the work that I did campaigning for the new law to recognise the posting of revenge pornography online as a crime, sometimes the law isn't straightforward in its application and new laws can help In the case of revenge pornography there are now more than 500 cases prosecuted a year.
"The issue of upskirting has been raised as part of the work of the women and equality select committee and we will be considering whether it should be included in a further inquiry into sexual harassment following our inquiry into sexual harassment in schools in 2016."
Sarah Green, for the End Violence Against Women coalition, described the figures as "very concerning, even though only a minority of police forces were able to respond because the behaviour is not classified as an offence".
She said: "The police responses show that the police are clearly struggling to recognise 'upskirting' distinctly, even though the disclosures reveal that it is commonly connected to existing sexual offences including voyeurism and sexual assault.
"It is notable that girls and young women are disproportionately targeted where that information has been recorded.
"Mobile phones have had a huge impact on the scale and types of offences committed against women and girls over the last few years and it is critical that the law and chief constables keep up with this. The law should be urgently examined in this area."