"We look forward to seeing this law change so that standardised packs can be implemented sooner rather than later."
New Zealand had been keeping an eye on the outcome of legal challenges against Australia's plain packaging, one from tobacco firm Philip Morris and another from tobacco-producing countries via the World Trade Organisation (WTO).
Australia won the case against Philip Morris in December.
The WTO challenge is ongoing, but Mr Key said he received advice late last year that the Government was on a "firm footing" to progress plain packaging because several other countries -- including the UK and Ireland -- had introduced it.
These countries did not face challenge under the WTO.
The Trans Pacific Partnership (TPP), signed on February 4, also allows tobacco control measures, so New Zealand could advance anti-smoking policies without risking a legal challenge.