Channel 4 has not apologized or responded to requests for comment after sharing the post - which has now been deleted - on its Instagram account.
The post featured the 'letter's board' from TV show Countdown, spelling out the phrase 'u asswipe'.
The caption accompanying the image said: "When your friend tells you they're doing Veganuary."
Despite numerous calls for an apology - and a slew of media outlets including PBN requesting a comment - Channel 4 has yet to publically address the issue.
According to charity Veganuary, which encourages people to try a vegan diet during January: "After Channel 4 published its anti-vegan message, many of the 500,000+ UK vegans responded.
"Hundreds of people messaged Channel 4 and commented on the post. They stood up for their rights, and stood against discrimination.
"The company later deleted its post, but at the time of writing, Veganuary, the UK-based charity, has received no apology."
Veganuary wants the broadcaster to acknowledge its faux pas, saying: "We are calling on Channel 4 to apologize to the vegan community, acknowledge the harm such comments cause, and update its editorial guidelines to ensure this never happens again.
"And we are also calling on the UK Government and legal system to crack down on anti-vegan hate speech, by protecting vegans to the extent the law requires.
"Vegans have a sense of humor. We have some of the best memes you'll find on the internet.
"But this isn't a joke."