A petition calling for a change in the law was set up after a Hertfordshire police dog and his handler were stabbed in Stevenage while chasing a suspect.
It is due to be debated in Parliament on Monday after topping 100,000 signatures in a month.
But the Home Office has said people who attack animals can already be jailed for 10 years so no new law is needed.
German shepherd Finn was stabbed in the head and chest and his handler, PC Dave Wardell, received a hand injury in Denton Road, Stevenage, after they pursued a suspect in the early hours of 5 October.
A 16-year-old boy from London has been charged with the assault of the officer and criminal damage relating to the dog.
A petition, set up on the UK government's petition site days after the attack, proposes that police animals "be given protection that reflects their status if assaulted in the line of duty" and has now received more than 120,000 signatures.
Responding to the petition, the Home Office said: "Under some circumstances assaults on support animals could be treated as criminal damage, allowing for penalties of up to 10 years' imprisonment.
"An additional offence dealing specifically with attacks on police animals may not result in more prosecutions or increased sentences."
But Mark Tasker from the Finn's Law Twitter campaign said: "The government's response is not that surprising. They must reply to any petition that achieves 10,000 signatures.
"We had a very positive meeting with the Home Office before the weekend and we feel confident that the government are reviewing all options.
"We believe we will see a new law within the next year."
Giving police animals the same legal status as officers injured at work is "unnecessary", the government has said.