Government-backed plans to give police dogs and horses extra legal protections from attack have been derailed after opposition from a Conservative grandee.
There were groans in the Commons as Sir Christopher Chope dealt a blow to campaigners after announcing he objected to the Animal Welfare (Service Animals) Bill.
The Bill, so named "Finn's Law" after a police dog brutally stabbed while protecting his handler, aims to remove a section of the current law of self-defence often used by those who harm a service animal.
The Bill was tabled by Conservative MP Sir Oliver Heald and would have progressed further towards becoming law if Sir Christopher, who has a reputation for derailing private members' bills, had not objected.
The rules in Parliament mean it only requires one MP to shout "object" to block a bill's progress once time for debate has concluded at 2.30pm on a Friday.
Sir Oliver said he was "disappointed" following the debate, but said he was "hopeful" upon the Bill's return to the Commons on July 6.
Speaking prior to the debate Environment Secretary Michael Gove had offered his full support.
He said: "This Bill will offer stronger protection for the many brave service animals that help to protect us.
"This Government is continuing to raise the bar on animal welfare, whether it be for our beloved pets, brave service animals or on farms."
Finn's handler Pc Dave Wardell, from Hertfordshire, said the dog - now retired - saved his life when a robbery suspect they were pursuing turned on them with a knife in 2016.
Finn was stabbed in the chest and head but did not let go until reinforcements arrived, and was initially thought unlikely to survive. But while the suspect was charged with ABH in relation to wounds to Pc Wardell's hand, he faced only criminal damage charges over the injuries to Finn.
"My boy Finn, now retired, was one of several thousand service animals that work to protect the whole of society 24 hours a day, every day," said Pc Wardell.
"When Finn was seriously injured it didn't seem right to me or the public that he was seen as an inanimate object or property, in law."
The Bill, if passed, would amend a 2006 Animal Welfare Act to address concerns about defendants' ability to claim they were justified in using physical force to protect themselves from a service animal.