Police have been accused of operating as "private security" at a Wellington defence industry expo, after declassified documents revealed officers were told to investigate any complaints made by delegates against peace activists.

A restricted document, released under the Official Information Act, reveals 101 police were deployed to the protest – codenamed Operation Faga – and issued with a tactical run sheet to be destroyed once the operation was complete.

The run sheet instructed officers to "undertake investigation into any complaints against protesters by delegation members" at the forum.

ROBERT KITCHIN/STUFF Protesters were pushed back by police to make way for delegates. (File photo)

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Police have defended the directive as within the scope of everyday policing, but human rights lawyer Michael Bott disagrees, saying the order seems to show a lack of neutrality and a bias towards delegates.

Fifteen protesters were arrested during fraught scenes outside the forum at Westpac Stadium in October.

KEVIN STENT/STUFF Nervous delegates entering the forum. Documents have revealed police were tasked to "undertake investigation into any complaints against protesters by delegations members." (File photo)

As busloads of delegates attempted to enter the stadium, a few hundred protesters, including groups from Auckland, blocked the entrances.

Bott said the directive to investigate any complaint against protesters suggested an invitation to delegates – regardless of the substance or legitimacy of any complaint – to come forward "at even a minor annoyance".

"It's almost like a fishing expedition ... the instruction seems to be to put discretion aside and investigate any complaint," he said.

SUPPLIED A restricted document, released under the Official Information act, shows officers were tasked to "undertake investigation into any complaints against protesters by delegation members," at Wellington's annual defence industry forum in October, 2017.

The directive showed an "excessive interest, bordering on the paranoid or hyper vigilant," Bott said.

He pointed out that police had, in the past, been prepared to "bend the law", citing the example of an illegal checkpoint used to target people who had attended a 2016 euthanasia meeting in Lower Hutt.

But operation commander Inspector Brett Amas rejected the idea police were on the side of the defence industry expo delegates.

CAMERON BURNELL/STUFF Human rights lawyer Michael Bott said the police directive seemed to lack neutrality and could be seen to show bias towards the delegates.

Police would follow up complaints from delegates the same as they would from other members of the public, he said. That did not equate to delegates having the power to trigger or prompt arrests.

The restricted document also shows firearms were to be readily accessible at the protest, in locked vehicles – but only carried in "extreme circumstances" – and that intelligence had been gathered on protest groups.

Protesters and police have had a strained relationship since 2015 after activists twice successfully went through the courts to have charges against them dropped.

KEVIN STENT/STUFF Police remove a protester, armed with a walkie talkie, from the stadium. Eventually 14 people were arrested.

In response to the question of whether deploying 101 officers to a lawful protest was good use of police resources, Amas said police actions were always dictated by the situation presented to them.

"Police respect the lawful right to protest. However, we must balance that against the public's right to go about their daily business safely, without being disrupted or put at risk by protest action."

Police would not say how much the operation cost.

Tom Hunt/STUFF Protesters blockade "weapons expo" at Westpac Stadium.

Peace Action Wellington spokeswoman Laura Drew said the Operation Faga order was "quite explicit that police took on the role of private security for delegates at the weapons expo, and that is concerning, even if it is unsurprising."

"Their approach to policing these events is inconsistent with the idea that the law applies equally to everyone," Drew said.

"The operation order specifically refers to following up on any complaints delegates have about protesters, whereas we know from experience that the police do not care about any violence protesters experience at the hands of delegates, or the police themselves."

KEVIN STENT/STUFF Peace Action protesters attempt to stop delegates entering the forum. (File photo)

The "heavy-handed and violent" actions of the police in protecting and attempting to escort delegates inside was shameful, she said.

Of the 15 people arrested, six were released without charge on the day and four are still facing charges.

KEVIN STENT/STUFF Peace Action protesters attempt to stop delegates entering the October defence forum at Westpac Stadium in Wellington.