Bill English says he doesn't know what the aim of Paul Moon's open letter is.

A group of 27 high-profile New Zealanders, including unlikely allies such as Don Brash and Dame Tariana Turia, have penned an open letter warning freedom of speech is under threat in the country's universities.

It was the brainchild of Auckland University of Technology's History Professor Paul Moon, and rejects "the forceful silencing of dissenting or unpopular views" on university campuses.

It also insists debate must not be suppressed because the ideas put forth "are thought by some or even by most people to be offensive, unwise, immoral, or wrong-headed".

PHIL WALTER/GETTY IMAGES Human Rights Commissioner Dame Susan Devoy is keen to see Police gather hate-crime statistics.

It comes after a group called the European Students Association at Auckland University was closed down after threats to its members and accusations of racism. Its leaders had denied it was racist.

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The letter also follows Human Rights Commissioner Dame Susan Devoy's February call for a review of "hate speech" law and Police Commissioner Mike Bush suggesting an examination of the pros and cons of a specific crime.

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The open letter has been signed by academics, business leaders, community representatives and controversial commentators including Sir Bob Jones, former prime minister Sir Geoffrey Palmer, Maori educationalist Sir Toby Curtis, poet Albert Wendt and former MP Luamanuvao Winnie Laban.

Moon said freedom of speech was the foundation of a modern, diverse and democratic society and it protected religious freedom and individual expression.

"Kneejerk calls from Police and the Human Right Commission to introduce hate-speech laws after recent attacks on ethnic communities will have the unintended consequence of suppressing free speech. Education, open debate and understanding will change racist and intolerant views – not censorship," he said.

DEAN KOZANIC/STUFF Former National leader Don Brash has joined Dame Tariana Turia in opposing restrictions on freedom of speech.

Freedom of speech was intimately connected with freedom of thought, he said.

"There is no inalienable right not to be offended. It is dangerous and wrong to silence someone because you take offence or don't like what they say. Of course there are limits; that is why inciting hatred or violence is already a crime."

The current law was working well.

JASON OXENHAM/FAIRFAX NZ Paul Moon, Professor of History at the Faculty of Maori Development at AUT coordinated an open letter defending free speech at universities

Police Minister Paula Bennett has poured cold water on the idea of a new crime, saying hate speech can be an aggravating factor in sentencing but going further was not a Government priority.

But Moon said Devoy's idea seemed to be her legacy project. "It's not dead in the water yet as far as we can tell."

In a speech at a Holocaust Remembrance Day event, Devoy said that free speech was one thing, hate speech another.

HAGEN HOPKINS/GETTY IMAGES Former Maori party co-leader Dame Tariana Turia one of 27 signatories to letter defending free speech.

"I believe online hatred is something we can get better at calling out. I believe we need better restrictions when it comes to the online forums" as well as social media accounts.

It was obvious to her when freedom of speech became a cover for threatening and harmful language.

She was also keen to see Police gather hate crime statistics.

Meanwhile Moon pointed to the forced closure of the European student club at Auckland University and threats to its members, describing it as a slippery slope to be wary of.

"History shows that fear and intolerance drives suppression of free speech, not that free speech causes fear and intolerance," Moon said

Universities must remain places for robust debate and the free exchange of ideas, not a place where unpopular views were censored.

But there was a "tsunami" with universities in the UK, Australia and the United States facing huge restrictions on freedom of speech.

"The question is when, rather than if, that happens here. Once it happens it's very difficult to undo, so we would like to head it off," he said.

"Where it becomes dangerous territory is where they criminalise ideas. Where they say if you criticise someone that potentially constitutes hate speech and therefore you shouldn't do it.

"And that goes against two or three hundred years of European tradition and even longer in the Maori tradition where divergent views are expressed and people reach a sort of synthesis eventually ... a unified or agree-to-disagree position in the end."

Being accused of hate speech would also "put a brand on your forehead - you are guilty of hate speech... without really knowing what your motives are or looking at the arguments".

"The preparedness of the state to curtail free speech in the (name) of either good race relations or order or whatever else is a very dangerous step. Because it doesn't actually solve any problem it, it really just suppresses it."

He said the signatories to the letter included those diametrically opposed on some issues, such as Brash and Turia on the Treaty and Maori rights.

"But what unites them is that they are all prepared to have their say and have others have their say, even if it's a very different imposing argument. That really is the essence of how free speech works."

Moon said he planned to send a copy of the letter to all party leaders in Parliament seeking their response to it."

It was not about influencing a particular statute, but his hope was "they will take that as guidance when they are considering any hate speech legislation".

Those who put their name to the letter were:

Assoc Professor Len Bell, Dr Don Brash, Dr David Cumin, Sir Toby Curtis, Dr Brian Edwards, Graeme Edwards, Dr Gavin Ellis, Sir Michael Friedlander, Alan Gibbs, Dame Jenny Gibbs, Bryan Gould, Wally Hirsh, Professor Manying Ip, Sir Bob Jones, Professor Pare Keiha, Assoc Professor Luamanuvao Winnie Laban, Dame Lesley Max, Gordon McLauchlan, Professor Paul Moon, Sir Douglas Myers, Assoc Professor Camille Nakhid, Sir Geoffrey Palmer, Professor Edwina Pio, David Rankin, Philip Temple, Dame Tariana Turia, and Professor Albert Wendt.