Greens Senator Sarah Hanson-Young Greens Senator Sarah Hanson-Young. Photo: Alex Ellinghausen

The Greens will attempt to force a vote in the Senate on plans to resettle in Cambodia refugees whose claims for protection are recognised on Nauru - and is challenging Labor to block any deal.

The party's immigration spokeswoman Sarah Hanson-Young is confident any deal with the Cambodian government will have to be approved by Parliament and has branded Cambodia ''a fundamentally unacceptable place for Australia to dump its refugees''.

Senator Hanson-Young is relying on qualified advice from the deputy clerk of the Senate, Richard Pye, suggesting any removal of those who came to Australia as ''unauthorised maritime arrivals'' to another country requires parliamentary approval.

But a spokesman for Immigration Minister Scott Morrison says any agreement with Cambodia would not involve transferring people from Australia, so would not require parliamentary approval.

The advice comes as the Cambodian government has confirmed that an agreement is imminent and could be signed within weeks.

Legislation providing for asylum seekers who attempted to come to Australia by boat to be sent to a ''declared country'' was introduced after the High Court struck down the Gillard government's plan to send boat arrivals to Malaysia.

While Manus Island in PNG and Nauru were designated as regional processing countries, Mr Pye's advice suggests other destinations for those sent to either country will need to be similarly designated.

In a letter to Senator Hanson-Young, he says it is not apparent to him that there is ''any other method'' by which a country may be designated as a destination for unauthorised maritime arrivals.

Cambodia's Secretary of State in its Foreign Ministry, Ouch Borith, told ABC radio on Monday that a working group had studied a proposal by Australia and would submit a counter-proposal ''maybe a few days, maybe next week''.

He said he hoped the agreement would be signed ''as soon as possible''.

While the designation of Manus Island as a country for regional processing is being challenged in the High Court, Senator Hanson-Young said the Greens were determined to block the ''secret, dirty deal with Cambodia'' in the Senate.

''The Abbott government needs the Parliament's approval to make this deal happen. Chest-thumping arrogance alone won't be enough and the Greens are ready to stand in his way,'' she said.

''It's unacceptable that the Abbott government is shaping up to send women and children to a country with a history of whippings, caning and electro-shock torture.''

Labor has refused to be drawn on the plan, with immigration spokesman Richard Marles, saying the party is reserving its position until it sees agreement details.