A four-month-old Labrador puppy called Bruce is fighting for his life after swallowing a suspected death cap mushroom in Griffith on Sunday.

His owner, Ben Jausnik, broke down in tears when describing the puppy's increasingly dire medical battle, saying the vet had told him there was now little more he could do on Thursday.

Bruce the Labrador puppy fights for his life after eating suspected death cap mushrooms. Credit:Ben Jausnik

"He is in really bad shape and I don't know if I can continue... to justify putting him through the pain," Mr Jausnik said, implying he may have to have the dog put down.

Mr Jausnik, who lives in Kambah, was over at his parents house in Griffith when he let Bruce off his lead briefly to stretch his legs while he was parking his car.