The announcement about its long-time head, Graeme Smith, was made by the Home's acting chief executive Vince Haining on Wednesday evening.

A Home spokeswoman declined to comment on whether Dr Smith stepped down voluntarily or was forced to go.

In a statement, Mr Haining said he expected many supporters to be surprised by the news. He thanked Dr Smith, who joined the home in 1986, for his contributions.

"He has been the face of the home for almost three decades and has had a significant impact on animal welfare and the way our community approaches responsible pet ownership. We wish Graeme well in his future endeavours," the statement said.

The state government is investigating the Home following a series of reports on its euthanasia rates and the revelation that a widow's pet dog, Fonzie, was put down by the Lost Dogs' Home the day after his owner had called to claim him in January.

One of two online petitions calling for an investigation into the shelter attracted almost 10,000 signatures.

Mr Vince said: "We have every confidence in our staff to ensure our practices and our policies continue to support the best outcomes for every animal in our care."

Agriculture Minister Jaala Pulford said in late January the government would investigate the home after she said had been inundated with phone calls, emails and messages on social media from people expressing their concern.

Ms Pulford said she had also been contacted by former staff at the home.