Animal Justice Party MLC Emma Hurst said many of the horse carcasses found on the outskirts of the city were brumbies and she wanted a parliamentary inquiry into "shocking allegations" an illegal knackery was operating at the location.

Wagga City Council has been leading a multi-agency investigation into the matter and said an inspection of the property indicated the slaughtering of horses had been occurring for a long period, with numerous separate dumps of dead horses found.

Council's general manager, Peter Thompson, said an estimated 500-plus horse carcasses had been located with "some no more than skeletal remains while others killed relatively recently".

Ms Hurst said rehomed brumbies counted for about half of the allegedly slaughtered animals.

Support for a multi-level investigation into the deaths was backed by Wagga MP Joe McGirr and Wagga-based Nationals MLC Wes Fang, who have described the situation as "appalling" and "incredibly concerning".

Ms Hurst called for further hearings as part of a current inquiry into the aerial shooting of brumbies in the Kosciuszko National Park.

"We have had confirmation that at least 260 of the animals were brumbies that had been indicated as rehomed," she said.

"There are unofficial reports that the number of brumbies may be higher.

"I will be calling for further hearings of the inquiry to investigate these shocking allegations."

Ms Hurst said community members had been left distraught amid allegations that slaughtered brumbies had been sold for greyhound and human consumption.

"The community is clearly very distressed and concerned about how this could have happened, and an open and transparent inquiry process is essential," she said.

"... There are a lot of unanswered questions."

Ms Hurst said a full investigation was needed by the upper house.

"This is beyond rehoming protocols, there has been a major failing in process and animals have suffered the fate of those failings," she said.

"How so many animals were ever so-called rehomed to one individual is highly questionable and the inquiry committee will need to examine who was involved and how this was ever allowed to happen."

A spokesperson for Environment Minister Penny Sharpe said she was seeking more information about a person who had been authorised to rehome wild brumbies between 2020 and 2023.

Ms Sharpe has also requested a review into the wild horse rehoming program.

"I am deeply concerned by the reports," the minister said.

I have asked the NSW Department of Climate Change, Energy, the Environment and Water to investigate the rehoming program.

"The NSW government is urgently bringing together relevant agencies and will provide further updates shortly."

Dr McGirr said he had spoken with the minister on Thursday morning and told her Wagga City Council was "not the agency best equipped to lead the investigation".

The MP said only a government inquiry could get to the bottom of the "very disturbing matter".

"A wide range of government agencies have been involved yet there has been no recognition that this is an important matter of public interest, no apparent co-ordination or details provided about who has been monitoring the process, and the government needs to do better," Dr McGirr said.

"This is a matter causing a great deal of distress to the community and it's essential that answers to these questions are provided as soon as possible and measures put into place so it can't happen again."

Dr McGirr said a "full, transparent inquiry" was needed to "provide the answers our community needs".

"We need to know how this was allowed to happen, where the horses were sourced from, in what circumstances they arrived at the property, what role government agencies have played, and who should be held accountable," he said.

Dr McGirr said it was also important to investigate whether some of the horses were feral animals taken from the wild and any inquiry should establish whether there had been a failure of the monitoring and supervision of the rehoming process.

"It's a sad fact that feral horses do need to be removed from the wild - under best animal welfare guidelines and RSPCA supervision - for the sake of the environment," he said.

"But we also expect that the rehoming of horses literally means finding new and safe homes under proper supervision with animal welfare paramount throughout the entire process."

Mr Fang said the National Party had long held concerns about "the lack of transparency around the Minns Labor government's management plan for brumbies" in Kosciuszko National Park and the incident had "reaffirmed those concerns".

The MLC - who has been on several committees looking into the aerial culling of brumbies in the national park - said revelations about the "makeshift knackery" were "incredibly concerning".

"The NSW government needs to be forthcoming as to the circumstances behind its establishment, operation and for what purpose it operated," he said.

"We are hearing a number of horses may be rehomed brumbies. If this is the case, the NPWS and RSPCA need to immediately be involved in the investigation."

The RSPCA declined to comment.

A property owner and the National Parks and Wildlife Service were also contacted by The Daily Advertiser.