Shocked commuters are reportedly being handed cards while travelling on the Tube, telling them they are a "fat, ugly human".
According to the cards, those responsible for the campaign call themselves 'Overweight Haters Ltd', an organisation that claims to "hate and resent fat people".
Kara Florish, 30, from Southend-on-Sea, was handed a card at Warren Street station by a "ordinary-looking middle-aged man" who then scuttled off.
She told Stylist magazine: "When I first read the card I thought it was a joke so put it on the seat next to me.
"I'm a size 12/14, what people call curvy but I don't consider myself fat.
"I'm active, go to the gym at least twice a week, don't smoke, hardly drink and don't do drugs. I have no health issues that I know of, have never been seriously ill or in hospital so don't consider myself a drain on the NHS. In fact, I'm currently employed by them."
Commuter Sean Thomas Knox says he saw a woman being handed a card, who then broke down into tears when she read it.
The card goes on: "We object to the enormous amount of food resources you consume while half the world starves.
"We disapprove of your wasting NHS money to treat your selfish greed. And we do not understand why you fail to grasp that by eating less you will be better off, slimmer, happy and find a partner who is not a perverted chubby-lover, or even find a partner at all."
The man handing out the leaflets is reportedly described as being an "ordinary-looking middle-aged man".
Transport for London is urging people to report any such instances to station staff or police.
A spokesman said: "All of our customers have the right to travel with confidence, and this sad and unpleasant form of anti-social behaviour will not be tolerated."