They range from shoestring outfits surviving on donations from elderly benefactors to professional enterprises with fundraising and marketing arms and paid research staff.

They seek to shape public opinion and influence policy-makers and politicians. They lobby vigorously, but have more strings to their bows than lobby groups. They call themselves think tanks.

Deeply enmeshed in the political fabric of the United States, Europe, Asia and Australia, think tanks are gaining a foothold in New Zealand.

Organisations such as the New Zealand Institute, the Maxim Institute, Motu, Ecologic and the Environmental Defence Society, while not quite household names, all aim to become one.

Although they lack the size, resources and influence of overseas think tanks, they are positioning themselves as experts on policy issues ranging from personal savings and a common currency with Australia to prostitution law reform.

There are two kinds of think tanks: those that focus on research for its own sake and those that use research to influence outcomes by involving themselves in policy debate.

The second category aims not just to push their point of view when occasion arises but to create the occasion. So they undertake and commission research, churn out papers, organise conferences, lobby politicians and policy-makers and feed opinion pieces to the media, with varying degrees of success.

How much notice we take of them depends on their credibility - it is important that we know them for what they are.

The Maxim Institute has garnered the most publicity recently, for all the wrong reasons. It describes itself variously as a social policy and research organisation or social policy think tank; non-profit, independent and funded by donations.

Set up four years ago, it has grown rapidly, employing 20 staff and becoming a prominent voice against prostitution decriminalisation, civil unions, the NCEA, hate-speech laws and proposed smacking legislation.

It has pushed its case through contributed articles in the opinion pages of newspapers, and by unveiling "research" and surveys on such topics as parental concerns about schooling.

Modelling itself on think tanks in Australia and the US, it has positioned itself as presenting an informed approach to public policy. Says its website: "Maxim performs timely, accurate research and analysis ... building and maintaining the institute as a trusted source of analysis and comment."

But revelations that the thoughts of director Bruce Logan were not always his own have considerably dented Maxim's credibility.

Logan, the institute's best-known mouthpiece, concedes he regularly plagiarised overseas commentators and commentaries without acknowledgment. His cut-and-paste penchant was exposed by the Association of Rationalists and Humanists (using a web-based programme which detects plagiarism), following the dumping by the Press in Christchurch of columnist Alexis Stuart, after a reader recognised lines in one of her columns from a previous article by Logan. Stuart, it turned out, was Logan's daughter.

The Press' response to the rationalists' findings was ominous for Maxim and a wake-up call to others.

"I suspect few editors would now touch them with a barge pole," said editor Paul Thompson.

"It does show how vulnerable newspapers are to this type of bad faith from contributing writers. It is no longer enough for newspapers to accept that their material is sound. Our checking systems will need to be vastly improved."

But the issue with Maxim is not just the integrity of its research, but the barrow it is pushing. Unlike think tanks with "pure" research motives, Maxim has been reluctant to identify itself for what it is - a conservative Christian group with a specific agenda.

Although journalists soon cottoned on, labelling them right-wing, conservative, even fundamentalist Christian when quoting them, their contributed articles carry tags such as "social research organisation" or "independent social policy think tank".

It is arguable that casual readers, wanting to bone up on civil unions or the NCEA's failings, remained none the wiser that the analysis came from a particular, conservative Christian angle. That's an issue for newspapers as much as for Maxim.

The challenge for the institute is to restore credibility as a think tank which promotes sound decision-making, as it promises on its website.

Maxim's high profile makes it exceptional among local versions of the think tank. Until its emergence, the Business Roundtable virtually had the Op-ed (contributor) pages of newspapers to itself, publishing research and wheeling out overseas experts.

It's not that our lobby groups don't have think tank aspirations - it's just that they lack the long-term guaranteed funding.

Peter Neilson, chief executive of the Business Council for Sustainable Development, says it takes a strong subscriber base or solid endowment to sustain a public good research component.

Professor Jonathan Boston, deputy director of Victoria University's institute of policy studies, says our small population means not only money is in short supply.

"There's not a great diversity of thought here. You do need critical mass to generate sustained debate."

Another constraint is the relative ease with which individuals and groups here can gain access to politicians and policy-makers.

One newcomer with genuine think tank ambitions is the New Zealand Institute. Spawned by the Knowledge Wave conferences, its broad-based membership includes Microsoft chief financial officer Chris Liddell, Oxford University vice-chancellor John Hood, The Warehouse's Steven Tindall, Deutsche Bank's Scott Perkins, Auckland City Missioner Diane Robertson and Onehunga High School head Chris Saunders.

Funding from membership fees exceeds $1 million and, says chief executive David Skilling, "while we don't have plans for world domination, we would certainly like to grow".

Skilling, a former Treasury economist, believes the group has already helped to influence Government policy with the Kiwisaver scheme and Working for Families package. But he insists it is politically neutral.

Ecologic, spawned out of the Maruia Society, is prepared to enter the political arena.

"We provide what we think is independent and robust research and analysis but are not shy about entering the policy debate ourselves," says senior fellow Jim Sinner. "Everyone has a position they come from - we try to be explicit about ours."

What secular groups object to about the Maxims is that they have not been so explicit. The maxims on the Maxim's website could mean many things to many people. Its mission: through policy and public debate to promote the principles of a free, just and compassionate society.

Who wouldn't sign up to that? Read further and you learn that the Maxims promote "an understanding of the institutions and principles that sustain a liberal democracy and civil society". These institutions are "the intergenerational natural family, voluntary associations, the church and the market. The critical principles are responsible freedom, the separation of powers and a limited government which protects the institutions of civil society".

And what's a civil society? It is "a way of understanding the relationship between the individual and the state that preserves both freedom and responsibility".

"State intrusion causes problems which then require even more government intervention. As more law restricts and controls us, we lose our freedom, and civil society is eroded.

"The family is the basic building block of civil society. ... Lifelong marriage between a man and a woman provides a foundation for strong families which other types of partnership cannot ... Yet the place of marriage has been consistently weakened in law over the past 30 years."

Happily, salvation is at hand. "Historically, religion has been the primary force that transmits ... the moral understandings essential to a liberal democracy. Churches foster values that are essential to civil society ... " And so on.

Any number of lobby groups would have a different take on the causes of our alleged social decline. Yet their views have not garnered anywhere near the same publicity, or meeting time with politicians and policymakers, as the Maxims have enjoyed since forming in 2001.

What makes them the envy of others is their funding and organisational strength. With offices in Christchurch and suburban Auckland, they have a $1.5 million budget.

Managing director Greg Fleming, formerly general manager of Christian-based Parenting with Confidence, says he spends two-thirds of his time fundraising by personally approaching individuals and community trusts.

David Hay, the former Auckland deputy mayor, is a significant contributor, as is Christchurch's Middleton Grange School, a Christian school where Bruce Logan was once headmaster.

Fleming says the institute has attracted 2000 donations to date and no single donor provides more than 5 per cent of funding.

Are they all Christians? "They see their lives as being informed not just by practical considerations but by an understanding of faith and values ... Most would describe themselves as conservative."

The ease with which the Maxims have used the media to push their case is an issue for the news media to consider. As for the Maxims, they're moving to improve on their advocacy and research activities. "It's important we listen to our critics," says Fleming.

Look out for wisdom on the failure of boys in schools and "comprehensive literature reviews" on family and marriage policies and the role of faith in building communities.

Should we expect impartiality? "I don't think there is such a thing as an impartial think tank. Everybody starts from a position of holding certain beliefs."

Think tanks as we know them

* The Business Roundtable

Often seen as a one-man band (Roger Kerr), the voice of market liberalism exerted considerable influence during the free market reforms of the 1980s and early-1990s. Funded by subscription, it commissions research, publishes papers and books, contributes media articles, arranges seminars and networks with business organisations. Kerr retains confidence in the BRT's role, telling the Herald last year: "I think the fact that the Government has made only limited steps backward shows a kind of influence."

* Institute of Economic Research

NZIER was set up in the 1950s with a brief to foster public debate and knowledge of the economy. Best known for its quarterly economic surveys and consultancy work, it continues to undertake public policy research, organise seminars and host visiting experts. Public good work in the past year included a cost/benefit analysis of a Government proposal to open private companies' books and papers on sustainable land transport, corporate governance and capacity issues. Funded by membership fees and consultancy work but "would welcome sponsorship" to do more public policy work.

* Motu Economic and Public Policy Research

Undertakes research and conducts regular seminars to improve understanding of issues ranging from climate change to labour market. Eschews consultancy work; funded mainly by Foundation for Research, Science and Technology.

* Environmental Defence Society

Undertakes research, publishes handbooks, makes submissions, and hosts conferences on topics ranging from landscape protection and biodiversity to climate change and oceans policy. Funded by donations and grants.

* Ecologic

Mission to promote sustain-able development through science, research and dialogue. Has small research staff; commissions others. Funding largely from FRST grants and subscriptions. Current projects include resolving conflicts between sustainability and democracy.