Consumers and businesses have been warned to be on their guard about bogus charity collectors claiming to be raising money for Comic Relief.
The Charity Commission said some fraudsters were jumping on the Red Nose Day bandwagon and making collections in supermarkets by using fake charity registration numbers.
A member of staff at Safeway's in Droitwich, Worcestershire, exposed the scam when they were contacted by someone wanting to raise funds at the store.
The organisation gave a fake charity name, Child's Wish, and a Comic Relief charity registration number. But when the supermarket contacted Comic Relief, they were told the charity did not exist.
Jon Deakin, the store's general manager, said: "I am pleased that a member of staff showed great vigilance in recognising that this was a bogus charity and that by informing the Charity Commission we managed to prevent the collection from taking place at our supermarket and others in the future."
David Rich, head of investigations at the Charity Commission, said: "The fact that someone phoned the supermarket quoting the Comic Relief registration number shows how plausible this scam is.
"We really want to see people giving to genuine causes on Red Nose Day. That's why it's crucial that supermarkets know how to distinguish between what's genuine and what's not."
The Commission is advising supermarkets and anyone donating over the weekend, to follow simple steps when approached by a fundraiser.
* Make sure the charity has a genuine registration number. This can be checked with the Charity Commission, via its website - www.charitycommission. gov.uk - or its contact centre on 0870 333 0123.
* Ask questions: has Comic Relief heard of the charity? How much of the donations raised will go to charity?
* Contact your local town hall or the Charity Commission on 0870 333 0123 if you still have concerns.
All registered charities are listed on the Commission's web site.