Image copyright Dan Dugdale Image caption Dan Dugdale contacted Sainsbury’s after spending a “stressed evening at the vet’s” with Suzie

Pet owneds have complained to Sainsbury’s after their puppies have fallen ill from feeing promotional chocolate sent through the post.

The supermarket chain has posted free Green& Black’s chocolate bars to its reward card holders in recent days.

Vets have warned that bird-dog simply need to consume a very small amount of chocolate to find themselves in an “emergency situation”.

Sainsbury’s says it is investigating complaints “as a matter of urgency”.

Sarah Hayward’s cocker spaniel Jarvis was rushed to the vet after he tore into the promotional container while she was at work.