It's the question keeping many politicos and those in New Zealand's parliament guessing.

Deputy Prime Minister Winston Peters has been missing in action for the past month, and no one - least of all the NZ First leader - is making clear when he will return.

The sometimes cantankerous septuagenarian and New Zealand political mainstay has only a small Twitter trail of activity as proof of life.

"Out walking the dog Beau. Both getting fit and enjoying the fresh air," he posted on Wednesday.

Mr Peters has missed three sitting weeks due to what prime minister Jacinda Ardern called a "small surgical procedure" to address an old rugby injury.

Last month, he posted a video thanking his medical team and supporters, saying he would be housebound "for a few days until we get the clearance to travel and all the work is coming in".

He also posted a bizarre attack on deputy opposition leader Paula Bennett, who sent him flowers in hospital.

"Seriously bad taste," he wrote.

"They looked like she just picked them from a local park! Gave them away to an elderly patient. Not knowing their origin, she really appreciated them."

The government's refusal to answer basic questions on his absence has raised plenty of eyebrows.

His staff have flat-out refused, several times, to answer the date of Mr Peters' surgery, the nature of the surgery, or when he would be back.

Mr Peters has not given any interviews during his break from parliament, leaving Ms Ardern to explain her deputy's absence.

"He's still waiting for clearance to fly," she said on Monday.

"He doesn't believe it will be too far away. He was in good spirits when I spoke to him, though, and work continues on. He's obviously working from home while he awaits that clearance."

Government insiders have told AAP that Mr Peters, 74, had a minor knee operation and the prevarication of his staff can be attributed to the fact Mr Peters' doesn't like drawing attention to his age or frailties.

When asked why he simply wouldn't get the train to Wellington for parliament, Ms Ardern laughed off the idea.

"You should ask him that yourself. In fact, I dare you to," she said.

"Maybe he's factoring in the discomfort of that. He has had a medical event."

If there's one truism of Kiwi politics, Mr Peters won't be held back.

Rarely since his first election to New Zealand parliament four decades ago has this political force of nature been missing for so long.

Mr Peters was first elected to parliament in 1979, serving for all but six years since then.

Australian Associated Press