Mr Pohiva was medically evacuated to Auckland from Tonga Wednesday afternoon.
The Prime Minister’s Media Adviser, Lopeti Senituli has confirmed to Kaniva News the passing away of Mr Pohiva.
Pohiva,78, had been admitted to the Medical Ward of the Vaiola Hospital two weeks ago and was being treated for pneumonia.
A government statement said that on Tuesday 10 September, the medical experts at Vaiola Hospital decided that he should be medically evacuated to New Zealand.
PM Pohiva had been diagnosed earlier this year with a liver complication and he successfully underwent a medical procedure at Mercy Hospital in Auckland.
Starting life as a school teacher, Mr Pohiva grew to become one of the stalwarts of Tonga's pro-democracy movement.
RNZI reports a constant thorn in the side of the monarchy and nobility, Mr Pohiva's lifelong battle for representation has seen him fired from the public service and charged with sedition.
But he maintained support among the people, who repeatedly voted him into the Tongan parliament after he was first elected in 1987, making him the longest-serving people's representative.
Photo Loop Tonga file