Householders have been targeted by fraudsters demanding bank details to pay fixed penalty notices for leaving rubbish by their bins.
Residents of Blackburn & Darwen received phone calls from people claiming to be from the council asking for payment of a £70 fine.
The council said one local resident was repeatedly asked for details as the fraudsters tried to pressurise him into giving the information.
Head of environmental health and trading standards Chris Allen said: If someone has left extra waste beside their bin they will receive a warning letter, known as a Section 46 notice. If they repeat the offence, they will be sent a fixed penalty notice by post.
"The council never phones residents to issue fixed penalty notices and the only time we would ask for bank details over the phone is when people have called us directly.
An urgent warning to people never to reveal their bank details to a cold caller has been issued by the councils trading standards team.
Image: Blackburn town centre, part of Blackburn and Darwen council