The Government says New Zealand's free trade deal with Korea may mean a ban on foreign buyers is impossible – regardless of the Trans-Pacific Partnership (TPP).
Labour says it will only support the TPP if it stops foreigners buying land here, which it claims is pushing up Auckland house prices.
But Prime Minister John Key says he doesn't believe a ban would be effective and tax measures are better. Regardless, the Korean Free Trade Agreement (FTA) stops that.
"Technically, if the Korean FTA wasn't there, then yes, it's also possible that TPPA would trigger that," he says.
"But first cab off the rank, if you like, is Korea."
With or without Labour's support, Mr Key says he has the numbers to pass the TPP legislation through Parliament.
Mr Key is accusing Labour leader Andrew Little of opposing the TPP to please the left-wingers in his party.
"If they don't support New Zealanders to compete and succeed in these big economies of the world and let them fight with both hands in front of them, rather than one tied behind their back, then they don't support New Zealand."
Mr Key says China's "most favoured nation" status means there can be no ban, regardless of the TPP – and that was put in place by Labour in 2008.