Rifat Asghar, 42, was eating a carrot and sweetcorn meal from the supermarket for lunch when a colleague spotted a fury lump.
The advanced nurse practitioner inspected the two inch long furball and was horrified to discover a leg and a tail, as well as what looked like an eye.
She took the salad back to the shop in Bradford, where she says she was offered a £5 voucher.
An investigation revealed the ‘foreign object’ was a baby weasel and staff offered Ms Asghar £100 in vouchers - which she turned down.
Asda said the animal must have been picked up in a field during harvesting, and passed through the factory without being spotted.
Ms Asghar said she had been traumatised by the experience and now has to spend extra time and money preparing her food.
She said: “It has caused me a lot of trauma. I initially thought it was a mouse, and for about a week afterwards I had weird dreams about mice coming out my mouth.
“They say it was in there from when it was harvested. What happened to all the checks done after that happened?
“If something like that can go through all their processes and checks it worries me.
“I has completely changed the way I shop now and I can’t buy any prepared food any more. I’m having to make it all myself. It was so traumatising.”
An email from a team leader at the supermarket said the specimen was sent for testing at a lab in London, which revealed it was a young common weasel.
The email said: “The specimen was very badly damaged, showing some skin, fur, a leg joint, a foot and tail.
“It was concluded that the complaint specimen was most likely the remains of a young member of the species Mustela nivalis, the weasel.
“It was not possible to determine where the specimen could have originated from due to the lack of distinguishing features.
“It is in the opinion of Insect Research and Development Limited that as these weasels would not usually come indoors, the specimen may have been accidentally harvested with one of the components of the salad.
“Unfortunately, despite our best efforts and process controls it appears the foreign body has been picked up from the field during harvesting and has managed to by-pass all our trained eyes and washing processes.”
A spokeswoman for Asda said: “We work hard to make sure our products are in the best possible condition for our customers to enjoy, so we’re very sorry that on this occasion we let Ms Asghar down.
“We would like to reassure our customers that we have strict quality control measures in place for our fresh produce, and since this incident arose in November last year, we have worked with our suppliers and growers to assess these measures and to understand how this could have happened.
“We have also apologised directly and offered a gesture of goodwill to both Ms Asghar as well as as well as her colleague, who originally purchased the product.”