New Zealand's most influential and connected directors are made up of a core group of 17 men and women, according to new research on New Zealand's director network.

Kevin McCaffrey, a former partner at PriceWaterhouse Coopers who now runs his own governance consultancy business, said he undertook the two-month research project because he believed there was a lack of understanding and clarity of the director network.

"There is a complete paucity of primary research of New Zealand's directors' network. This gives rise to comments like there is an old boys' network."

Based on a study of boards in Britain, McCaffrey analysed the directors on 350 New Zealand organisations to look at the degree of separation between directors, how clusters of boards are connected and where each board is positioned in New Zealand's board network.

The research revealed a core cluster of 54 boards, which McCaffrey narrowed down to 24 which he said formed the core of the director network.

McCaffrey said it was interesting to note that the board of TVNZ was a connector board between other major companies and that Mighty River Power - a state-owned energy company due to be listed on the stock exchange next year - had a number of very well-connected directors.

He also analysed how many boards each director sat on. Of the 1428 directors, 86 per cent sat on just one board.

McCaffrey said that showed only 15 per cent acted as interlocking directors.

The numbers reflected international trends but he said it was concerning that so many directors sat on only one board.

"[This] is a worry because they do not have the chance to build depth to their governance experience."

He found 61 directors sat on three or more boards, with one male director sitting on seven boards.

The research also revealed that the proportion of women increased with the number of board positions held.

Of the total 1428 directors, 13 per cent were female. But of the 61 directors who sat on three or more boards 24.5 per cent were female.

Looking more closely at the 24 core boards, and ranking directors on the number of boards they sat on, produced a list of 17 people.

McCaffrey said there was a group of recently retired chief executives at the core of the network.

They included former Progressive Enterprises managing director Ted van Arkel, former ANZ boss Sir John Anderson and former Foodstuffs managing director Tony Carter.

McCaffrey said the small number of directors with influence was not surprising given the small size of New Zealand's capital markets.

"It gives us a glimpse of the potential to influence board appointments, connectivity that provides for investment floats, and the potential for brokerage about knowledge of people and brokerage of knowledge within a network," he said.

McCaffrey said he believed a board should reflect the demographic of the market it was serving.

"If you are in retail you should reflect the diversity and demography of the market. It ensures and aids the voice of the market being served."

McCaffrey said he intended to repeat the research on an annual basis and hoped to do a breakdown of age and ethnicity in the future.

The core 17:

Joan Withers, Mark Tume, Susan Paterson, Tania Simpson, Bryan Mogridge, Alison Paterson, Ted van Arkel, Hugh Fletcher, John Anderson, Tony Carter, Rick Christie, Elizabeth Coutts, Selwyn Cushing, Trevor Janes, Bruce Irvine, James Miller, Keith Smith.