Cox, who is also the youngest contestant for this year’s series, announced her Bake Off news on her social media pages.
She wrote: “I am so passionate about ethics and feel completely blessed to have the opportunity to share this with the world. To say I am the first completely vegan baker on GBBO feels like such an honour.
“I will be posting loads of updates, bakes and behind the scenes pics over on my Instagram page if you’d like to follow me on there. Speak to you all soon...the future really is vegan.”
The student, 19, from North Yorkshire, who is the first vegan baker to appear on the series, appeared to delete a Facebook page called Freya Cox Eventing, according to Mail Online.
The page was dedicated to her horse riding achievements but trolls suggested equestrian sport is cruel and she was therefore not a dedicated vegan by participating in it.
It was soon flooded with comments criticising her for riding horses.
Among a sea of comments, one wrote: “The problem people like myself are having is that, yes it’s great that someone is going onto a mainstream programme promoting vegan food.
“But please don’t say that you are passionate about ethics when you still ride horses. I know she still rides as she replied to someone on her Instagram earlier today saying they should meet for a hack soon!
“So just say that you’re plant-based and making slow changes to becoming fully vegan in future or something if that is what you’re doing. Saying that you’re passionate about ethics and then riding horses is completely contradicting and confusing.”
A second added: “Yep, she’s not vegan. Just plant-based obviously.”
However, there were plenty of comments supporting the star.
Others wrote: “I’m shocked at some of the comments on here, they’re shameful and unnecessary, can’t wait to watch you blow the others out the water.”
“Instead of seeing this as a great step to show non-vegan viewers what they can make and possibly help people eat more plant-based foods AND congratulating this girl, you find fault!
“Oh to be the perfect vegan, we are all trying.”
The Standard has reached out to Channel 4 for further comment.
Earlier this week, judge Paul Hollywood spoke out against contestants being trolled online.
Hollywood said trolling “can damage people”.
The TV judge previously came to the defence of 2020 finalist Laura Adlington as he blasted the “disgusting behaviour” of vicious online bullies.
Bake Off was filmed earlier this year. Like the 2020 series, all contestants and crew created a Covid-safe bubble to protect everyone during filming.
Bake Off season 12 will debut on September 21 on Channel 4 at 8pm.