A vegan woman has been left "traumatised for life" after she was served a sausage roll with meat in it.

British vegan Sharleen Ndungu bought the snack from UK bakery chain Greggs which launched a vegan sausage roll earlier this year.

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Ndungu only realised the mix up when she bit into the pastry and tasted real meat - and she says her body went haywire.

The 20-year-old says she "burst into tears" when it dawned on her she had been given two pork sausage rolls instead of the vegan ones.

"I haven’t had meat in two years. My belly started hurting and my heart started going crazy," she said.

"I was panicking because that only happens when I consume meat – this doesn’t happen when I have other food.

"I’m traumatised for life now – I’m never going to Greggs again."

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Kent Live reports that the store's manager offered her a 2-pound refund ($A3.63) but Ndungu did not think that was good enough.

She called the chain's customer line and was offered a 30-pound voucher ($54.50) but refused that too.

She then took to YouTube to make her case in a since-deleted series of videos.

"I was asking for a public apology to make people aware that they should watch out for things like this,” she said.

“People can be allergic to pork and potentially die from such a stupid mistake.

"It’s my choice not to consume meat because it causes cancer. That choice has been taken away from me.”

A Greggs spokesperson said the chain was investigating to make sure a similar mistake would not happen again.