A poster appealing for help finding “missing” six-year-old girl Amy Hamilton has been shared thousands of times on social media – despite being a racist hoax by a right-wing propaganda group.

The fake appeal uses a painting taken from a Flickr account to represent the fictional little girl, and underneath it includes the message: “It is believed Amy has been kidnapped by an Asian grooming gang.”

The poster is the work of the right-wing group Britons against Left-Wing Extremism (Bale), and was first spread as if it were genuine by the organisation’s blog and social media accounts branded the Daily Bale.

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Last year the Croydon Advertiser revealed that there was no Amy Hamilton, and that Daily Bale editor Steven Sodholmy believed he was “raising awareness… about the harsh reality of Asian grooming gangs”.

Yet that has not stopped the “missing” poster resurfacing, and this week it has been shared thousands of times on Twitter and Facebook.

One social media user who tweeted the image later wrote: “Turns out that pic was a hoax! I had no idea when I posted it!” He added that it was nonetheless “refreshing to see so many people care enough about someone they never met”.

Posting on at the weekend, Facebook user Chris Jopp said: “A friend shared this and I had to tell her it was a hoax.” Another, Lisa Charman, said: “Yep, I just got this hoax today in my newsfeed.”

When the fake appeal was first being shared, Daily Bale contributor Joshua Bonehill tweeted: “An amazing 5000 people shared our Amy Hamilton, Missing poster on Facebook. Lets (sic) hope they catch the Asians responsible for taking her.”

Mr Sodholmy said: “The poster and the 20,000 that shared it on Facebook were informed about the harsh reality of Asian grooming gangs that have been operating in the Croydon area of London now for some time.”

But Croydon police told the Advertiser: “These types of hoax appeals are, at best, extremely unhelpful and distasteful and can potentially divert public attention away from genuine appeals.

“We rely on the support of the public and media to help us when we release appeals to find our most vulnerable missing people.

“The support we get for these appeals is fantastic, but these hoaxes can really damage the effectiveness of genuine appeals.”