Dogs classified as menacing by breed will now be required to wear a muzzle at all times including private homes.

Christchurch dog owners are furious after being told they must muzzle their "menacing" pets even inside their own house.

The city council's animal management unit sent a letter to 159 owners of dogs classified as menacing – either by breed or because they have attacked or shown aggressive tendencies – outlining the animals must be muzzled at all times, unless secured in a cage or vehicle.

"[That] includes on your own property and includes within the dwelling house," the letter said.

Iain McGregor / Stuff Abbey van der Plas rescues unwanted dogs and owns two classified as "menacing" because of their breed.

Abbey van der Plas, who founded Christchurch Bull Breed Dog Rescue, was among those who received the letter. She said it was "outrageous" to think she would be required to muzzle her american pitbull even when it was sleeping at the end of her bed.

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"I can't even fathom who's idea it was to interpret the legislation in this way," she said.

Iain McGregor / Stuff The Christchurch City Council has changed its interpretation of menacing dog rules, and now says they must be muzzled at all times - including inside owners' homes.

Council chief executive Karleen Edwards said recent dog attacks prompted the council to seek legal advice around its interpretation of the dangerous and menacing dog classifications under the Dog Control Act.

Since March 2017, the council had been asked to investigate 234 complaints about dogs attacking a person, stock, poultry or domestic animals, she said.

"In the council's interpretation, a menacing dog is 'at large' when it is not tied up, or it's unchained, or unconstrained, even when it is inside a house or on the owner's property," she said.

"We acknowledge that this letter has come as a surprise, because of the interpretation that is now being applied. We are urgently seeking further legal advice on this interpretation to ensure we are doing the right thing."

Five breeds are automatically classified as menacing: Brazilian Fila, Dog Argentino, Japanese Tosa, American Pit Bull and Perro de Presa Canario.

Van der Plas said the council had taken the term "at large" too far.

Full time muzzling of dogs would breach the animal welfare act, she said.

"It's just disgusting they would expect a dog owner to subject their dog to that," she said.

"Animals need to be free to be able to display natural behaviour. How can a dog display natural behaviour when it's mouth is covered up?"

She said her group was meeting with animal welfare lawyers to discuss their legal options.

"We will fight this tooth and nail, no matter what we will fight it. We are more than prepared to fight it in court if we have to."

Irresponsible dog owners were the problem – not the dogs, she said.

Van der Plas said the introduction of muzzling within the home meant responsible dog owners were unfairly being targeted.

Christchurch pitbull and american staffordshire owner Stevi Gerard said the muzzling rules were "an absolute joke".

She said a pitbull's behaviour came down to "how they are brought up".

"They can be vicious but so can any other dog."

Edwards said while legal advice was sought she hoped all dog owners would meet the requirements of the menacing and dangerous dog classification.