Actually it was National, not Labour, that got Australia to exempt NZ from ISDS

The Herald reported:

The Investor-State Dispute Settlement (ISDS) no longer applies to investor screening.

Anyone who takes up contracts with the government would have to sue under domestic procedures instead of ISDS and a third aspect has been agreed around financial services.

Those provisions have been suspended, so while they will remain in the deal, a separate side treaty notes that they would not apply unless all nations agreed to re-include them.

As well as the reciprocal agreement with Australia to scrap ISDS provisions Ms Ardern said New Zealand was also continuing to seek side letters with a handful of other countries, but won’t detail who they are until an agreement has been ratified.

That implies it was an initiative from this Government to do an agreement with Australia to scrap ISDS provisions. But Richard Harman at Politik reports:

That is confirmed in a little-noticed section in the TPP National Interest Analysis produced by the Ministry of Foreign Affairs and Trade in January last year which said: “Consistent with ANZCERTA and the Australia-ASEAN-New Zealand FTA, TPP’s ISDS provisions would not apply between New Zealand and Australia. “

Notice of this was posted as an “associated document” to the TPP on the MFAT website in late 2015.

But speaking in Sydney on November 5, after her meeting with Australian Prime Minister, Malcolm Turnbull, Prime Minister Jacinda Ardern appeared to suggest that the pair had exchanged letters agreeing not to invoke ISDS procedures against each other.

“We discussed a signed letter on the ISDS clauses which we see as being mutually beneficial,” she said.

“That acknowledges our positions on ISDS – at least between each other.”

The exchange of letters (if it was new) was not necessary; MFAT had already established that the ISDS clauses did not apply to Australian investment in New Zealand.

So Labour tried to spin that the agreement with Australia was something they achieved, when in fact it was National that had negotiated it in the original TPP.