Four elderly people were tricked into handing over a total of more than £20,000 by “unscrupulous” fraudsters posing as police officers.
A woman in her 80s conned out of £12,000 was among those targeted in Thornton Cleveleys and Fleetwood, in Lancashire.
Victims were phoned and asked to withdraw cash before handing it over to a “courier”, police said.
Lancashire Police has warned people to be “extra vigilant”.
Det Insp Mark Riley said it was a “devastating scam” which targeted the vulnerable.
“These are unscrupulous offenders with no morals and are only interested in bringing misery during what should be a festive time, which is difficult enough during Covid restrictions,” he said.
Police said they stopped another woman in her 70s from being swindled after family became suspicious of a mysterious phone call.
Det Insp Riley added: “The victim was prevented from handing over her savings. But there were unfortunately three other incidents where victims have sadly handed over large sums of cash.”