Radical changes will be made to New Zealand's diplomatic postings with many appointments of ambassadors being opened to outside competition and even advertised in the newspapers, Foreign Minister Murray McCully signalled last night.

And he wants to make it easier for business and professional people to volunteer their services in New Zealand's development work, especially in agriculture.

Mr McCully has already upset New Zealand's foreign affairs officials by advertising the position of High Commissioner to Kiribati in the newspaper.

He has appointed non-career diplomats to plum posts: former Prime Minister Mike Moore to Washington, former National leader Jim McLay to the United Nations; and former chief executive of Customs Martyn Dunne to Canberra.

In a radical departure from tradition, he secured the appointment of its chief executive John Allen, who was formerly the chief executive of New Zealand Post.

Last night in a speech in Wellington to the New Zealand Institute for International Affairs Mr McCully promised to step up the trend.

The ad for Kiribati, he said, "is the overt signal I have sent so far that heads of mission roles - ambassadors and high commissioners - are not the exclusive preserve of staff of the Ministry of Foreign Affairs."

"My job is to enhance New Zealanders' interests overseas, not to keep the [diplomatic] union happy.

"Very simply, we are taking the approach that we will pick the best person for the job."

More ambassadors will be appointed as new missions are opened, such as in Africa where New Zealand has only two embassies in a continent of 53 countries, and some closed.

But costs will be cut by renting rooms in other embassies and engaging more local staff instead of sending Ministry of Foreign Affairs staff.

In another challenge to the way MFAT has rewarded seniority, he said he wanted younger talented people from the middle ranks of MFAT promoted to heads of mission roles.

He said the ministry had a track record of losing too many talented younger people because they had been forced to wait too long for opportunities.

Mr McCully continued his criticism of his own ministry by saying it had not done enough to encourage the development of specialists, particularly in the Pacific.

"I have made plain my view that New Zealand should boast the most expert and connected group of officials on Pacific matters of any foreign service in the world."

He complained the $63 million costs of administering New Zealand's $500 million aid budget was too high. He wanted more aid delivered through partnerships with non-government organisations and a model was being developed to make it easier for more New Zealanders to be part of the Government's development work.