Number of unreported cases likely to be far higher as individual losses range from £50 to £240,000

More than 200,000 people in Britain may have been conned by fraudsters posing as would-be romantic partners on internet dating sites, according to the first study examining the potential scale of the problem.

Anti-fraud groups have warned for some time about scams, in which criminals create a false identity – often an army officer on active service, explaining an inability to meet in person – and develop a close online intimacy with a victim, who is then asked for cash to help their presumed suitor out of a crisis.

It had long been suspected that official figures for such crimes greatly under-represented their prevalence, largely because many victims feel too embarrassed or hurt to go to the police, or never realise they have been conned.

The study by the universities of Leicester and Westminster, working with the Serious Organised Crime Agency (Soca), found 2% of people surveyed personally knew someone who had experienced the crime. Extrapolating this to the online UK population means more than 200,000 potential victims.

Monica Whitty, a psychologist and professor of contemporary media at Leicester University, said that the pool of those targeted was likely to be greater still as it did not include people who realised what was happening before they lost money and those who still did not realise they had been conned.

The researchers had been "shocked" at the numbers involved, she said.

There has been an assumption that victims tend to be middle-aged women. However, said Whitty, targets were from both genders and all age groups.

Aside from the financial costs involved – Soca has tracked individual losses ranging from £50 to £240,000 – those conned also faced the heartbreak of discovering that the person with whom they had fallen in love was the invention of a skilled con artist, usually Nigerian or Ghanaian, and often not even of the same gender.

"A lot of people find it very hard to accept what has happened, even if they know the person involved is now in jail," Whitty said.

"We've had male victims who still refer to the other person as 'she', even though they now know it was a man.

"In a few cases they've found the relationship so therapeutic they keep it going, even if they know they've been conned."

The scams often begin with an online dating site profile carrying a notably attractive photo, taken from elsewhere on the internet, and a description of someone in a remote, hard-to-contact location – whether a military base in Afghanistan or, to tempt male victims, a UK or US nurse at a small foreign hospital.

The use of almost exclusively online communication – the criminals occasionally resort to phone calls but these are rare given the extra difficulty of explaining away an accent – can actually accelerate intimacy, Whitty said, allowing victims to project their own hopes and desires on to a warm and empathic correspondent.

"Email and instant messaging can have the effect of being hyper-personal. Lots of people get in touch with someone through a dating site, meet them a few weeks later and this person doesn't live up to their expectations. With an online relationship this never happens."

The faked romances can last for a long time – the longest the researchers heard of was five years – with each criminal juggling a series of parallel relationships. At some point comes the request for urgent financial assistance, often to help them out of supposed difficulty.

"They might test the waters by asking for a present, for example saying they've lost their mobile phone and need another one. If this happens, they'll ask for money. It's like a clever marketing ploy."

Very few cases are seemingly reported. A spokesman for the UK's National Fraud Authority said the agency had learned of 730 crimes over the past 15 months, totalling £8m in losses.

The survey, covering more than 2,000 people, found that just over half were aware that such romance scams existed.

While this was a positive sign, Colin Woodcock of Soca said, significant numbers of people remained at risk.

"The perpetrators spend long periods of time grooming their victims, working out their vulnerabilities and when the time is right to ask for money," he said.

"By being aware of how to stay safe online, members of the UK public can ensure they don't join those who have lost nearly every penny they had, been robbed of their self-respect, and in some cases, committed suicide after being exploited, relentlessly, by these criminals."

How to spot a dating scam

Soca has compiled a list of tell-tale signs for people to look out for if they suspect their internet suitor is a con artist.

• A distant location and/or a job in the military: by pretending to be serving in, for example, Afghanistan, or on an oil rig, the scammer has a convenient excuse for being unable to chat on the phone or in person. When men are targeted, the other party often tends to be a nurse working in a remote country.

• A fondness for Windows Messenger or similar applications: aware that dating sites are increasingly conscious of such cons, the perpetrators can be keen to continue their wooing elsewhere.

• A suspiciously attractive and/or rugged-looking photo: of course, not every good-looking person lurking on a dating site is a fraudster. But the con artists tend to select particularly alluring physical alter egos, which they borrow from elsewhere on the internet.

• A quick adoption of a pet name: if, by the second email, you are being addressed as "dearest fluffy bunny", beware – it could be a fraudster looking to establish instant intimacy.

• A predisposition towards financial or other misfortunes: it is perhaps the most obvious tip, but if a suitor you have never met suddenly crashes their car, or needs an expensive airfare or a lawyer, be on your guard. The same goes if they start alluding to gold bullion or suitcases full of cash they hope to bring to the UK.