Joan Boyer, from High Brook, was with her family on Saturday night when she made the gruesome discovery.
The 77-year-old went to make her English springer spaniel Lexie her food which was the usual Tesco Everyday Value brand.
“I opened the tin of dog food and it was crawling with maggots,” she said.
“We had the family round with us and they were having their tea and I showed them. I don’t think they thought to much of it.
“You don’t expect to see it moving when you open the tin. I was very surprised and shocked.”
Joan bought the tin from the Tesco store in Burgess Hill a couple of weeks ago.
She said it was completely sealed before she opened it and had a best before date of 2018.
She said: “It was an innocent looking tin of dog food but wasn’t quite so innocent when I opened it.
“The lid was slightly bent but I just opened it as normal. It is obvious they must have been in there when it was sealed.
“They (Tesco) said bring it back to the store and we will send it to the head office in Scotland.
“I have never had any trouble before, I have been buying their dog food for years.
“I want more than my pound back for all the trouble.”
She added she would not be buying it again.
Luckily for Lexie Joan had more food in the cupboard.
Joan said she had reported the incident to trading standards and was awaiting a response.
A Tesco spokesman said: “There’s nothing more important to us than the quality of our products so we were concerned to hear about this.
“We would like to thank Mrs Boyer for agreeing to return the product to our store so we can investigate the complaint with our supplier.”
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