Transport for London and British Transport police have urged commuters to come forward if they have received so-called fat-shaming postcards on the tube.

Images of the leaflet, claiming to be from a group called Overweight Haters Ltd, have now been shared thousands of times on social media, with many speculating it could be a poorly judged publicity stunt.

British Transport police (BTP) said they were investigating reports of cards being handed out but could not elaborate as to whether victims had complained directly.

Kara Florish, 30, from Southend-on-Sea, shared on social media a picture of a card given to her by a stranger as she travelled on the tube that said: “It’s really not glandular, it’s your gluttony.”

Overweight Haters Ltd is not registered at Companies House, but pictures of the card and of Florish have been posted on image-hosting website Slimgur, which describes itself as “the internet’s premier shitlord image host”.

Shitlord is internet slang originating from the website Reddit to describe online activists who oppose acceptance of people who are overweight. The site appears to have been set up following the Reddit controversy over the removal of fat-shaming forums like /r/fatpeoplehate from the site.

Though many on social media have pointed to the site as being behind Overweight Haters Ltd, it is unclear whether the Slimgur posts are from the cards’ organiser. The only images posted on the site are those circulated by Florish on Twitter and Facebook.

On the opposite side, the card reads:

On Facebook and Twitter, Florish wrote: “I was handed this card this morning on the underground and I would appreciate if people tweeted, posted etc all over the internet.

“I am not upset myself. I am smaller than the national average and not exactly obese, but this is hateful and cowardly and could potentially upset people struggling with confidence and eating disorders. Please tweet and share this if you are also outraged. Plus – to the person who wrote this card, go back to school, you can’t spell ‘beautiful’.”

She said the man was middle-aged and white, and placed the card on her lap as he got off the carriage.

Another commuter, Sean Thomas Knox, described a similar incident on his Twitter account, though giving a different description of the man involved. “Young man just got on train at Oxford Circus, gave printed card saying YOU’RE FAT to overweight girl. He jumped off. She read it, [and] cried.

“Am 99.9% sure this wasn’t staged. She didn’t even realise I was watching at first. Her stunned, desolate reaction was very real. Then tears.”

Knox described the man who handed over the card as a “hipster.. smartly, trendily dressed” with a beard. “Perhaps it was a piece of conceptual art,” he tweeted

“It lasted a few seconds, but the card in that photo [Florish’s] is the same card I saw, in the girl’s hand. And her shock was real.”