People who fall victim to boiler room scams by purchasing virtually worthless shares lose an average of £20,000, the Financial Services Authority has found.
And it is even worse for Midlands investors.
The FSA surveyed callers to its consumer contact centre who had reported being targeted by boiler rooms - overseas operations that use highpressure selling techniques to persuade UK investors to purchase shares.
Boiler rooms are not authorised by the FSA and act illegally by promoting and selling shares in the UK.
In the majority of cases, it is claimed, the shares are worthless and the boiler room vanishes, leaving the investor out of pocket. And because boiler rooms are based outside the UK, the FSA is usually unable to take direct action to shut them down.
But it has mounted an ongoing campaign to raise awareness of the scam.
More than half (58 per cent) of respondents to the survey had fallen victim. Of those, 13 per cent had been conned by more than one boiler room while three victims each reported losses of over £100,000.
Jonathan Phelan, head of retail enforcement at the FSA, said: "Boiler rooms can be lucrative operations that fraudulently earn serious money. £20,000 is a shocking sum and far more than most people can afford to lose.
"Sadly, victims are unlikely to see their money again because their shares will have been overpriced and nearly impossible to sell. Boiler rooms are not authorised by the FSA, and are based abroad outside our reach, so victims are not protected by the financial services compensation and complaints schemes. Our strongest tool is to make people aware of the scam."
The survey found that boiler rooms tend to prey on older people.
Of those who had fallen victim to boiler rooms, 38 per cent were aged over 60 while 26 per cent were 51-60 years. The majority were male (81 per cent) and most were experienced investors with 41 per cent saying they had been doing so for over 11 years.
In England, most victims were from London or the South-east, but the Midlands was a close second.
The Scots and Irish fared even worse.
The survey found that 31 people had been targeted in London and the South-east, with 20 falling victim, losing an average of £21,823.
In the Midlands and East Anglia the equivalent figures were 25, 12 and £23,714.
Many victims reported that the boiler room repeatedly called to encourage them to invest. While 15 per cent were persuaded to purchase shares during their first call, nearly half (49 per cent) were called four or more times before they succumbed.
Regardless of whether they purchased shares or not, 63 per cent of respondents reported that they were pursued by the boiler room for at least one month and nearly a quarter (23 per cent) said they were receiving calls from the same boiler room for more than six months.
Mr Phelan said: "Boiler room salesmen won't take 'no' for an answer. They will constantly call a target, trying to build a relationship and get their confidence. They will appear knowledgeable and highly professional but they are only interested in taking your money."
Many of those caught out (57 per cent) reported that they were first contacted by the boiler room out of the blue on the telephone. Boiler rooms may also use a marketing firm to reach targets on their behalf.
The people behind boiler rooms often move from operation to operation taking lists of targets with them - a quarter of respondents said they had been approached by four or more different boiler rooms.
Although boiler rooms do not necessarily operate from where they say, the most common countries listed were Spain (29 per cent), the US (20 per cent) and Switzerland (20 per cent). Anecdotal evidence also suggested that Eastern European countries were popular locations for boiler rooms.