Some 44% of Londoners have been victims of bank card fraud and 42% have had their identity stolen, according to an Infosecurity Europe survey.
Researchers said the average amount stolen was £1,448 per victim, and 37% did not get their money back from the bank.
Those who lost smaller amounts were less likely to get their money back than those who lost larger amounts, the survey of 1,000 London commuters found.
Most people (91%) who lost more than £5,000 were refunded, compared with only 41% of people who lost less than £100.
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Some 60% blamed retailers for making them vulnerable to fraud, while only 12% blamed the banks, and 28% said it was their own fault.
More than a quarter (27%) said their details had been stolen through websites or e-mail, while a fifth said they lost their details during face-to-face transactions.
Being duped over the phone was the third most likely place to have details stolen with 15% of details being stolen this way.
Other ways that details were taken included cashpoint machines, online banking and letters being intercepted in the post.
Most of the affected (58%) were targeted in the UK, but 42% said the fraud happened to them while they were overseas.
More than half of respondents that were subject to fraud or ID theft said their credit rating was worse as a result, 37% said they had stopped online banking, and 34% said they had stopped shopping online.
Infosecurity Europe 2010 takes place at Earls Court, London, from 27-29 April.