Overseas buyers will no longer be allowed to purchase existing homes in New Zealand, Prime Minister-elect Jacinda Ardern declared as she unveiled a raft of policy deals made with her coalition partners.

The move to tackle soaring property prices was agreed during lengthy negotiations between the Labour Party leader and populist powerbroker Winston Peters to form a new government that also includes the Green Party.

Ardern announced plans to slash immigration on Tuesday and focus on regional development and job creation.

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New Zealand Prime Minister-elect Jacinda Ardern. Source: AAP

"We have agreed on banning the purchase of existing homes by foreign buyers," she said, specifying that the new rules only applied to non-residents.

"[We] also have plans around farmland and other critical infrastructure," she added.

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New Zealand First leader Winston Peters says his country is 'no longer for sale'.

Anti-immigration campaigner Peters, whose support was crucial for Ardern to form a ruling coalition in the 120-seat parliament, said a message has been sent that New Zealand was "no longer for sale".

The New Zealand First (NZF) leader -- set to be deputy PM and foreign minister in the new government -- ended weeks of negotiations when he confirmed last week he would use his party's nine seats to ensure a Labour, NZF and Green coalition with a three-seat majority.

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