A burglar stole from an 80-year-old woman while pretending to be a police officer investigating a previous theft from her home a month before.
The man phoned to say he had arrested someone for the first raid and asked her to check the garden of her home in Sidmouth, Devon, for missing jewellery.
After being sent out to look a second time, she returned to find a handbag containing cash and cards was stolen.
Police described the incident as "the lowest of the low".
The handbag was stolen from a downstairs room, but the woman found that a search had also been made of an upstairs room during the robbery on Wednesday.
Pc Sharon Newman, of Devon and Cornwall Police, said: "These people are the lowest of the low. They have no morals and we would love to catch them and put them before the courts.
"It is also of concern to us that this man has phoned saying that he is a police officer.
"We would ask anyone receiving such a call to check with the police before taking the sort of action this lady took. Saying that it is not a criticism of this victim, she was excited at the thought of getting her property back."
The force said it was unlikely that an officer would ask someone to check for stolen items as investigating officers would want to check the property and surrounding area for any evidence.
Police also warned that such attacks were not usually in isolation and warned the elderly and anyone with elderly neighbours or relatives to be extra vigilant.