Police Commissioner Howard Broad's job could be split into two or three roles, he said yesterday when announcing his retirement in March next year after five years.

The police commissioner role combines two other roles: chief constable and chief executive. The roles have not been separated but there was talk when Mr Broad was appointed that they could be separated, and he said yesterday it could happen next time.

The chief constable is the person who is the head of the police force, and is ultimately responsible for all policing and cases.

As chief executive he is responsible for the assets and a budget of $1.4 billion.

Mr Broad said the commissioner's role was "rather amorphous" and required him to maintain the all-round confidence of the public in the institution that is the police.

Two deputy commissioners, Viv Rickard and Rob Pope, are expected be contenders for police commissioner or chief constable.

Mr Rickard is the first Maori deputy commissioner.

Mr Pope headed the controversial Marlborough Sounds murder inquiry into the deaths of Olivia Hope and Ben Smart and is now head of police operations.

Mr Broad said apart from his predecessor Rob Robinson, no commissioner's term had been extended since 1981. "I was not pushed," he said. "I made the call with the minister months ago."

The role had put a lot of pressure on him, his family and his health, he said.

"I was pretty focused on completing one term. I didn't want to stagger on bit by bit. I have a clear programme of work that I set out to undertake."

Mr Broad said he was not the police commissioner who would reap the benefits of things implemented during his tenure.

"There is the unique experience of carrying a cellphone with you 24/7, whether you are in the country or out of it, that goes at very regular intervals with every piece of disaster, tragedy, every police officer that gets into trouble, every major inquiry that's made of the police, and you are expected to be right across that and be able to converse and interact on that at any time."

Mr Broad, a 35-year police veteran, was appointed commissioner in 2006.

He joined the force as a cadet in 1975 and later graduated with a law degree from Victoria University in Wellington.

He said he would write a book about the war service of a close relative and spend more time with his partner, Robin, and family. "I'm still a young man," the 53-year-old said.

Maori Party co-leader Pita Sharples said he thought Mr Broad was a good commissioner but was still unhappy with the 2007 terror raids on Maori and other activists.

"I don't think the Tuhoe episode was well done," Dr Sharples said.

"I'd rate him up the top. I think he's been pretty understanding [of Maori], flexible, well more understanding really cause of the way he's dealt with our leaders, and of course I had him in Auckland [as district commander] and have seen him first hand.

"We recommended him, actually, to be the commissioner."

- Additional reporting by NZPA