More than one in five over-55s suspect they have been targeted by an investment scam in the past three years, according to research from the City regulator.
A survey of people aged over 55 who have a household income of £30,000 and/or savings of £5,000 found that 22% had been contacted by a person or organisation that they believed to be making a fraudulent investment offer in the last three years.
Among those surveyed who were aged over 75 years old, nearly one in three (32%) believed they had been targeted by an investment scam in the past three years.
The Financial Conduct Authority (FCA), which released the findings, is urging over-55s to take the time to check that investment "opportunities" are legitimate before they hand over their money.
It said that, on average, victims of investment fraud lost £32,000 typically last year.
The new pension freedoms, which give over-55s a wider range of choices over how they use their pension pots, make this group a particularly attractive target for fraudsters.
Low interest rates giving poor returns on savings may also tempt some people to take a risk with their cash, with the promise of better potential returns.
The new research is part of the FCA's ScamSmart campaign, which helps to protect consumers against investment fraud.
The most common check people tended to carry out before investing in a financial product was to look at a company's website, the survey found.
But the FCA warned that investment fraudsters and unauthorised firms can create highly professional-looking websites to entice people.
TV presenter Nick Hewer, who is supporting the ScamSmart campaign, said: "I have been targeted by these scammers myself so I'm not surprised to see how many other people have also been approached.
"The amount of money that is being lost by victims is extremely worrying, which makes it all the more important that this issue is tackled.
"If you are contacted by someone offering an investment out of the blue, just put the phone down. The FCA Warning List is a fantastic resource for those who are unsure about an investment offer - in a nutshell, check, check and check again."
Mark Steward, director of enforcement at the FCA, said: "Making a significant financial investment is an important decision - be prudent, do your homework and be especially on guard if contacted out of the blue by someone you don't know.
"Fraudsters are targeting our growing over-55 population because they are more likely to have money to invest. They may pressure you to make a quick decision or try to make you feel stupid for not taking up their bogus offers.
"No investment decision should be rushed. Be sceptical. Be suspicious. Ask questions and get answers you can verify."
More than 1,000 people aged over 55 took part in the survey.
In the recent Autumn Statement, the Government announced plans to ban pensions cold calling. Under the proposals, calls where a business has no existing relationship with someone will be forbidden. The next steps will be announced in 2017.
To avoid becoming the victim of an investment scam, the FCA suggests that people do the following:
:: Reject unsolicited contact about "investments".
:: Check the FCA Register to see if a firm is authorised and check the FCA Warning List of firms to avoid
:: Get impartial advice before investing.