"She's a little Maltese who's 17-years-old and blind who resides in my laundry most of the time," he said.

"I took her outside and was watching her when I got distracted by a phone call, and when I finished the call she was gone."

Despite constantly searching the area during the day and checking with the Domestic Animal Services (DAS) and RSPCA lost pet sites, Mr Gvozdanovic was unable to find Izzy.

But a phone call the next day would prove to be even more distressing.

Mr Govzdanovic was told by a Canberra vet that Izzy had been brought into the clinic by DAS staff, where the vet was ordered by DAS to euthanise the dog, only 24 hours after she had gone missing.

The order from DAS staff came despite DAS policy stating that impounded dogs are required to be held for seven days, with dogs either re-homed, sold or euthanised after this period.

Emails seen by The Canberra Times from vet staff to Mr Govzdanovic said they initially refused to euthanise Izzy, saying despite the dog being old, she was in a healthy condition.

"We do see rather a lot of stray injured and sick dogs, some of which are euthanised for humanitarian reasons, but Izzy does not seem to have been one of those," the email said

"[Izzy] did not appear to be life-threateningly unwell on presentation and it was felt her discomfort could be managed."

Vet staff said despite the directive from DAS to euthanise Izzy, they felt it "was not animal cruelty to care for Izzy overnight".

"Records indicate that a call was made to DAS the following morning advising that [DAS] should not pick up the body as the dog had not been euthanised as per instruction," the email said.

"This apparently led to a lively response from DAS demanding Izzy be euthanised on animal welfare grounds. [Staff] did not feel able to refuse in face of an insistent and demanding person from DAS and complied with the directive."

Mr Gvozdanovic said he was devastated when he heard the news from the vet.

"I'm deeply upset at my pet being killed, I'm just in disbelief that this is how my pet came to its end," he said.

"I regarded Izzy as a member of the family.

"I didn't pursue Izzy more aggressively because Izzy had been found by DAS I had seven days to get in touch, so I had faith in the process."

ACT Opposition urban services spokeswoman Nicole Lawder wrote to City Services Minister Meegan Fitzharris on Friday about the situation.

"Could you please advise as a matter of urgency how this sad event has taken place within hours of a much loved elderly family pet going missing," Ms Lawder wrote.

In a statement, a Transport Canberra City Services spokesman said Izzy was in "poor health" with its coat "highly matted" when it was found by DAS staff.

"Both DAS and the treating veterinary practice attempted to contact the owner via the details found on the microchip, however the recorded details were not current and after a number of attempts contact was unsuccessful," the spokesman said.

"After further liasion between DAS and the treating veterinary surgeon, the dog was euthanised.

"DAS are currently investigating the matter further, including talking with the owner."