Some elderly householders are being targeted by people offering to sell them bogus "energy saving" devices that are dangerous.
Trading standards officers say they have received more than 200 complaints about phone calls from the scammers.
The callers claim to be energy suppliers, or their partners, and offer a plug-in gadget that supposedly cuts electricity use by 40%.
The officials say they are unsafe and could cause a fire or electrocution.
Ron Gainsford, chief executive of the Trading Standards Institute, said criminals were using high energy prices as a pretext for selling dangerous devices, mainly to elderly householders.
"A safety recall has been issued for the items traced so far," he said.
"[We] have had a number of the items tested which not only failed to satisfy electrical safety standards but do not deliver any tangible energy savings."