There have been reports of 'Nottingham Knockers' operating in South Gloucestershire, the Lansdown area of Bath and parts of Bristol.
These are cold callers who usually tell residents that they are ex-offenders trying to go straight, then try and sell poor quality and over-priced cleaning products.
An email sent out to residents said: "The police want to remind residents they are under no obligation to answer the door to anyone they don’t know or aren’t expecting.
"If you do talk to them, they are supposed to be able to provide a valid Pedlar’s Certificate and should leave your property when asked."
"Police always recommend using a door chain and asking to see the identification of unexpected callers."
Other advice includes calling 999 if you are suspicious of a caller, keep your cash in the bank, not at home and keep windows and doors secured if you’re not in the room.
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