A vegan in the UK is hitting out at a bakery chain she claims poisoned her by accidentally giving her a meat sausage roll instead of a plant-based one. 

Sharleen Ndungu ordered two of the Greggs vegan sausage rolls from the Canterbury city centre branch in Kent, KentLive reports.

She said she realised it was pork when her body began reacting to the meat as she ate it.

"Heart palpitations like I was running somewhere or something," she said in a YouTube video.

"And then my stomach started turning upside down, I was like 'woah, what's going on, this only happens when I consume meat'."

Ndungu said she instantly burst into tears and believes there will be lifelong complications from her eating the meat.

"My body is poisoned for life now, you know," she said.

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She went back to the store and demanded an apology. She said staff offered her a £2 refund for the money she spent on the rolls but it was not enough.

"If I was allergic to pork or any of the ingredients that were inside that dirty sausage, I literally could have died.

"Some people, namely meat-eaters, might think I'm over exaggerating but I could have died."

Ndungu contacted Greggs' head office, who offered her a £30 voucher which she says she turned down.

She said she was sharing her story to encourage people to check what they had been given was what they wanted before eating it.

A Greggs spokesperson confirmed it's investigating how the mistake happened.. 

"We have apologised to the customer for this incident. We are investigating to ensure this situation can be avoided in the future."

Ndungu has vowed to never return to Greggs again.