ACT public servants employed on an ongoing basis must be citizens or permanent residents, while those on temporary contracts must have a valid working visa.

Public school cleaners are currently employed by four companies, who between them hold eight contracts for the ACT's 87 public schools.

But as of January, the government will move to directly employ school cleaners.

Education Minister Yvette Berry spoke about the move to in-house cleaning during ACT Estimates hearings on Monday, leading to criticism from the Canberra Liberals.

Opposition spokesman for business and employment Andrew Wall said her comments showed that migrants might lose their jobs because of the decision to terminate cleaners engaged through small businesses.

"To be employed in the public service you have to be an Australian citizen or permanent resident," Mr Wall said.

"This means many cleaners from refugee or migrant backgrounds may be the first to miss out on permanent employment because of this policy.

"Often refugees or migrants who are new to Australia gain quick employment in cleaning services.

"We should be making it easier to employ migrants and refugees, not harder."

But Ms Berry rejected the suggestion migrant and refugee workers could lose their jobs. "The government will offer employment to all current public school cleaners who are legally entitled to work in Australia and meet ordinary pre-employment checks," she said.

"For current school cleaners who are citizens or permanent residents, their employment offer will provide permanent ongoing status.

"For current school cleaners who are in Australia on a temporary visa, their employment offer will provide non-ongoing status for the duration of their visa - equivalent to their current right to work in Australia. I am disappointed that Mr Wall would so recklessly attempt to create uncertainty for a group of vulnerable workers that the government has been working to protect."

Ms Berry previously said the move to in-house cleaners would protect vulnerable workers, pointing to the large number of migrants cleaners.

"For example, a large number of these [cleaners] are from the S'gaw Karen people group and now live in Canberra after fleeing conflict in Myanmar," she said.

About the decision to move in-house, she said "high standards for ethical, industrially-compliant employment" were unlikely to be met through an outsourced service.

"Achieving these high standards is difficult in the cleaning industry, where margins are tight and the services are homogeneous. The required contract management has also proven very demanding," Ms Berry said.

She said the rates of pay and conditions for school cleaners would be "broadly comparable" to what they were currently on.