Vanessa Franco said staff told her she 'should have known it was chicken'. (SWNS)

A vegan mother has hit out at KFC after staff at the fast-food chain served her a chicken burger and then “laughed at her” when she complained.

Vanessa Franco attempted to order the restaurant’s new vegan burger at a drive-thru in Colliers Wood, London.

But after three bites she realised something wasn’t right and confronted staff who told her it was in fact chicken.

According to Franco, KFC employees laughed when she told them she was vegan and asked why she didn’t notice it was chicken.

The incident took place at a KFC drive-thru in Colliers Wood, London. (Google)

Franco, who recently turned vegan and has been a life-long vegetarian, said: “I realised the texture tasted different.

“I drove back to KFC and asked them to confirm it was a vegan burger. That’s when the girl who served me told me it was a chicken fillet burger.

“She then called her colleague who told me to come inside.

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“She also said if I took bites out of it then why didn’t I notice it was a chicken burger. I explained I have been a vegetarian my whole life.”

Franco then went into the restaurant to speak to the manager.

A KFC restaurant sign from a different location. (Matthew Horwood/Getty Images)

“That’s when he gave me a vegan burger, didn’t apologise and laughed and said, ‘You should have known it was chicken,’” she added.

“All of the staff stood there staring at me. I felt humiliated and have been left traumatised due to not only a lifestyle choice but also religion being broken and made fun of.

“I was speechless and can’t express how disgusting their customer service was.”

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KFC later apologised for her ordeal.

A spokesman said: “This isn’t great and we’re really sorry for what happened here.

“Our vegan burger launched last month and we took its arrival seriously – putting strict new processes in place to make sure it’s served properly, including the use of separate coloured tongs and storage units.

“We’re following up with the team to remind them of the importance of getting this right and will be offering the guest a free meal on us to put things right.”