Opposition parties have mixed feelings about NZ Post selling 45 percent of its subsidiary Kiwibank and there are concerns about its future ownership.
Finance Minister Bill English says because the buyers, ACC and the Superannuation Fund, are Crown entities, the bank will remain 100 percent government-owned.
The Government is also guaranteeing that if any of the shares are sold, which the buyers will be able to do after five years, it will buy them back.
Green Party co-leader James Shaw has a problem with that.
"It would be interesting to see if a finance minister, in five years' time, would agree with a statement made by a finance minister today," he said.
"Bill English can't bind a future finance minister to that statement, so it's an empty promise."
Mr Shaw says his party is concerned that moving part of the ownership could create "a slippery slope to privatisation".
Labour leader Andrew Little described the share sale as "a clever scheme" which would give Kiwibank an opportunity to raise capital.
The party's state-owned enterprises spokesman, David Parker, says a Labour-led government would commit to buying back shares.
ACT leader David Seymour says it's an odd, in-house partial privatisation.
"The taxpayer will still bear all the risks of investing in a bank," he said.
"Selling part of Kiwibank to other government entities is a compromise on a compromise."
Mr Seymour says it would have been "braver and better" to sell part or all of Kiwibank to private owners.
"Sadly, we witness another episode of National campaigning from the right and governing from the left."
Kiwibank is valued at $1.1 billion, which means that when the deal is finalised NZ Post could receive $495 million.
It needs the money. Its core mail business is declining and it can't afford to put any more capital into Kiwibank.