Police in Portsmouth want to hear from anyone in the Copnor area who has recently had cold callers offering to work on their property.
The appeal follows bogus callers from a company claiming to be Fair Trade, of Southampton, who have taken £46,000 from a man in his 60s.
The victim was told the money was to strip off paint from the outside of his house, that had been mixed with asbestos, and repaint it.
Money was taken on nine separate occassions, between late August and the end of September, to carry out the work, police said.
Yet no work was carried out.
Police believe Fair Trade is a fictitious company created to dupe customers. Officers would like to hear from anyone who thinks they may have been approached by the bogus callers, or if they think they may know who they are.