State health ministers will push back against a federal government plan to outsource aged care assessment teams in a Council of Australian Governments meeting on Friday, calling for the government to postpone the change until after the aged care royal commission is completed.

Guardian Australia understands that New South Wales and Western Australia will present a joint paper to the health minister, Greg Hunt, outlining their concerns at Friday’s meeting of health ministers, while Victoria has already decided that it will not partake in the proposed new model.

Federal Labor has been targeting the Coalition over plans to outsource aged care assessment teams, which are currently undertaken by state-employed health workers funded by the federal government.

The aged care minister, Richard Colbeck, has denied that the proposal, to come into effect next year, will privatise the workforce, despite saying the tender process would be open to both government agencies and the private sector.

While there is broad support for merging both the aged care assessment teams and regional assessment services, the states and aged care peak bodies have raised concern about the shake-up of services that could see new providers contracted for the work.

A letter from the Victorian director of ageing and aged care, Jackie Kearney, obtained by Guardian Australia, says the state is still hoping to retain the current model that gives it jurisdiction over the delivery of a state-wide streamlined assessment service.

“However, should the tender proceed as outlined by the commonwealth, the department will not be tendering to provide assessment services under the new model,” the letter says.

The department raises a particular concern that the commonwealth proposal aims to have “multiple providers” in each service area.

The paper from WA and NSW is understood to raise similar concerns, with no single provider – including state governments – to be able to have more than 50% of the assessment work in any one region.

It also highlights the large number of assessments undertaken in state-run hospitals, with concerns that a third-party provider would take longer to undertake the assessments than currently achieved by the states.

The paper also calls on the federal government to delay its proposal until after the aged care royal commission reports later this year.

Labor’s shadow minister for aged care, Julie Collins, said the government should use the Coag discussion to “come clean on why it would want to privatise these assessments and outsource this work”.

“There is already an experienced, well-qualified and highly-trained workforce undertaking aged care assessments across the country,” Collins said.

“It makes no sense to make this decision before the final report of the aged care royal commission is released in November.”

In January, the royal commissioner into aged care, Gaetano Pagone, issued a statement clarifying that the commission had not supported the privatisation of Acat assessment teams, objecting to suggestions from Colbeck that it had done so.

“Public concern has been expressed about statements made by the minister for aged care and senior Australians that we had decided to support the privatisation of the aged care assessment teams in our interim report,” Pagone said.

“I take this opportunity to make clear that the interim report did not endorse the government’s stated position but noted that we would monitor with interest the implementation which the government had announced,” he said.

In parliament on Thursday, Colbeck said the government currently did not directly procure any assessment service in the aged-care sector, subcontracting to state governments and 17 other providers.

“What the government has said it intends to do is to create a single assessment workforce. That is exactly what we intend to do. I have never conceded that the government’s intention is to privatise, as the opposition continue to claim, because that has never been our intention,” Colbeck said.

“We will continue to work very closely with state and territory governments to ensure that senior Australians get the assessment service that they need as they enter into the aged care sector.”

The One Nation senator Pauline Hanson also told the Senate she had been assured by Colbeck that there would be no privatisation of aged care assessment teams.

“I have been given an ironclad guarantee by minister Colbeck that the Morrison government has no desire to privatise ACAT.”