By Karen Sweeney

New Zealand should hold out for a better Trans Pacific Partnership deal that includes blocking offshore buyers purchasing existing residential homes, Labour's finance spokesman Grant Robertson says.

The government on Thursday approved a mandate for negotiating a new TPP agreement with the remaining 11 nations after the US pulled out earlier this year.

Trade Minister Todd McClay is hopeful a proposed version of the agreement will be put to leaders at November's APEC leaders meeting in Vietnam.


But Mr Robertson says now is an opportunity for New Zealand to renegotiate a better deal.

"Australia has protected for itself exactly the proposal we are making around making sure that offshore buyers can't buy existing residential homes," he told TVNZ's Q&A program on Sunday.

"This is not about wishlists, this is just about getting New Zealand the same deal out of TPP that Australia's got."

But in an economic debate Finance Minister Steven Joyce argued renegotiating would take years, and it's through existing rules that Australia secured that commitment rather than through the TPP talks.

"Australia had that long prior to TPP - the deal actually is that everybody continues with their previous laws unless they change them," he said.

"New Zealand has one opportunity with the TPP. If we choose, along with everybody else, to say we want to renegotiate this, that and the other thing then TPP will take years."

Mr Joyce said currently between two to three per cent of homebuyers and sellers were offshore, meaning the net increase was "virtually nil".