The investment fraud costing victims £26,000 each
A growing investment scam is resulting in fraud victims losing an average of nearly £26,000 each, according to City of London Police.
It involves so-called binary options trading, where individuals can bet on share price or currency movements.
Victims are being encouraged to go to the trading websites through adverts on social media.
The Financial Conduct Authority (FCA) has already warned about binary options, which are not regulated.
In the first half of 2017, nearly 700 victims lost £18m, according to police.
That means average losses of £25,916 each.
A police spokesperson said the fraud is affecting a wide range of people - not just those with financial backgrounds.
'I have no purpose'
One victim from London, Jamie Norton, lost £300,000 on binary trading - all his money.
"They just sucked me in with all their communications and promises," he told the BBC's You and Yours programme earlier this summer.
He was forced to sell his home as a result. And he has been left with lasting emotional damage.
"Every night I don't want to wake up the following day," he said.
"I have no purpose to get up for. There's nothing that I enjoy. There's nothing that I look forward to."
How does binary trading work?
Investors do not buy the shares themselves; they simply bet on whether they are going to go up or down.
If they choose a call option, they are betting a particular share price will rise over a given period of time. If the share price is higher at the end of the contract, they win. If it is lower, they lose.
If they choose a put option, they are betting the share price will fall.
The same principle applies to bets on currency movements, or share price indices.
Some of the sites are legitimate, according to the Police, but many are not.
Earlier this week the police and Trading Standards visited 20 addresses in the City to investigate such fraud.
Some of the websites are thought to operate from prestigious addresses in the Square Mile, although others are based abroad.
In one case, they found evidence of a firm that had disappeared, despite having paid three months rent in advance.
"This multi-agency operation allowed us to speak with multiple businesses and gather significant intelligence around various investments currently being traded in the City," said chief superintendant Glenn Maleary, head of the Economic Crime Directorate at the City of London Police.
"With our partners, we want to ensure the City is a hostile environment for fraudsters to operate in and we will continue to do everything we can to ensure that this is the case."
In some cases the websites use celebrities to entice people in. Both Sir Richard Branson and Martin Lewis - the founder of MoneySaving Expert - have found their photographs being used to promote the scams.