Mr Lauwers said he believed Jagger has been purposefully targeted, saying: "There is no other option, it had to have happened [at Crufts]. How can you mistakenly poison a dog?
"Jagger was such a promising dog. He was just 3 years old but he was well known around the world. Of course, if you are successful, success doesn't make you a whole lot of friends."
Mrs Lauwers said "strange things" had been happening in the months leading up to the show. Of the suspected poisoning, she said: "I am convinced it happened at the dog show. There wasn't any other opportunity. It looked like an act of jealousy."
After celebrating with their dog's co-owners, Dee and Jeremy Milligan-Bott, the Lauwers made their way back to Belgium on Friday afternoon, arriving home in Tongeren around midnight.
"I prepared food for the dogs and I called Jagger to come over. He just collapsed and started shaking, it looked like a fit," Mrs Lauwers said.
"We called our vet immediately. He started having diarrhoea and urinating on himself. It looked like a heart attack. He went into a coma a minute later and died. I called the vet and she said it looked like poison."
The couple took their dog straight to the clinic for an autopsy. Jagger's stomach was found to contain pieces of meat. "Inside there were small colours - white, dark green and black. The vet is convinced it is poison, possibly a few different types to make it work more slowly but efficiently," Mrs Lauwers said.
Mrs Milligan-Bott, from Leicester, urged her fellow competitors at Crufts to "unite in finding the perpetrator who did this", and warned that no one should leave their dogs unattended at the show. Fears about dog safety at Crufts deepened on Sunday night as one judge said that two ladies had told her they believed their dogs had been poisoned.
Gillian Barker-Bell, the judge for Irish setter dogs who placed Jagger second in class on Thursday, said: "I can't believe anyone could be so evil or vindictive. Dogs have been tampered with at other championship shows so this is not a first. But I have never heard of a dog actually dying. What a sick mind to do something like that."