The Labour Party is urging the Prime Minister to lobby the Australian leader Julia Gillard to improve the treatment of New Zealanders living across the Tasman.
Ms Gillard arrives in Queenstown later on Friday for talks with John Key.
The meetings will celebrate 30 years of Closer Economic Relations between the nations, but there are sticking points in the relationship.
Labour's foreign affairs spokesperson Phil Goff says it is unfair that New Zealanders living long-term in Australia don't get welfare support while Australians living in New Zealand do.
Mr Goff says this is the big issue for the Prime Minister to raise with Ms Gillard.
Mr Key says the matter is likely to be discussed, but he is not going to tell the Australians how to treat New Zealanders living there.