"I only have got a very small amount in my office and once that runs out I'm aware supplies are very short."
However Mr Key told Firstline this morning that he also likes the Australian-made rival Vegemite.
"I've got to be honest, I can eat both."
Jars of the black gold have already been listed on Trade Me, with bids for a 250g jar at $63 this morning, with proceeds going to Cure Kids.
Sanitarium general manager Pierre van Heerden said people should consider spreading it on toast rather than uncooked bread to make it last.
"With toast, it's a little bit warmer so it spreads easier and it goes a little bit further," he told Radio New Zealand.
"So what we're asking consumers is maybe if they could have their Marmite on toast, ration it a little bit, maybe have it only once a day or every second day until such time as we can have full Marmite stocks back out in the marketplace again."
Mr van Heerden said there was still some stock in retailers' distribution centres and on supermarket shelves.
"Certain sizes have totally run out and last week, at the end of last week, we sent our last stocks out to the distribution centres of the retailers."
But he urged consumers not to "freak out about it".
"We will get Marmite back, we will be producing it in New Zealand, it will be the same product that we've all come to love."
Mr van Heerden said a manufacturing tower at Christchurch the plant had been severely damaged in the earthquakes and was in the process of being deconstructed.
"What we've been doing since we discovered that is working really hard and our prime focus has been to make sure we can get our Marmite plant relocated into a safe area on-site."
Deconstruction of the tower was proceeding well, he said.
Is your local supermarket running out of Marmite supplies? Help us map New Zealand's Marmite shortage:
