Journalist Selene Nelson had reportedly emailed William Sitwell in the hope of pitching a series of features on plant-based meal ideas - to which Sitwell replied: "How about a series on killing vegans, one by one?"
He then followed up by asking if Nelson had ideas on how to trap them, force feed them meat and "expose their hypocrisy".
— Nick Chowdrey (@nickchef88) October 29, 2018
Shocked by the response, Nelson took the story to Buzzfeed and said in an interview with the website: "I've written about many divisive topics, like capital punishment and murder cases and domestic violence, and I’ve never had a response like that to any of my articles or pitches.
"And he's the editor. He’s representing Waitrose and he’s talking about 'killing vegans, one by one'?"
The writer added that she'd never seen anything like it and that if Sitwell wanted to continue hating vegans, that was "his prerogative", but added that for him to have that attitude while representing Waitrose is "seriously bizarre".
The MasterChef critic has since apologised after being contacted by Buzzfeed News.
Several people are already calling for a boycott of the supermarket chain until he is replaced, while one person has even gone as far as to create an online petition to have Sitwell removed.
At time of writing, 554 people had signed it.
User @MathieuKervyn wrote: "Dear @waitrose. As a regular customer I find the comments made by William Sitwell shocking and completely unacceptable.
"I hope you deal with this appropriately, as this will reflect your position on bullies and abusive behaviour."
@dab_actor said: "@waitrose you’ve just lost me as a customer after William Sitwell comments. Absolutely disgusting what he said and the fact you’re still dithering over whether to sack him shows your abject leadership and incompetence."
While @niphette added: "I’m certainly not a vegan but William Sitwell’s 'joke' was.. just really bizarrely gratuitously violent? I mean it’s not normal to respond like that to a stranger with a professional request, is it? In this case it’s not the offensiveness so much as the weird familiarity implied."
Buzzfeed editor posted a Tweet stating that a Waitrose spokesperson had said the chain will be "taking up the matter" with their editor.