The controversial Taser trial is again under fire with the chief ombudsman saying reports by police about the use of the device have been "sanitised".

The 12-month test of the 50,000 volt Taser stun gun is now over with Police Commissioner Howard Broad due to make his decision on their implementation within months.

But in a letter to Broad, Chief Ombudsman Beverley Wakeham says the police wrongly withheld information from its reports about the 20 times the Tasers were fired during the trial period.

The reports have now been released to the public under freedom of information laws.

Wakeham says the police have provided summaries of those incidents but she has described them as being "extremely brief" and having the overall effect of "sanitising the original reports".

The criticism has been welcomed by anti-Taser campaigners such as lawyer Marie Dyhrberg.

"The police have not been open and transparent. They have been very selective about in what information they have decided to provide to the New Zealand public," she says.

Police have always been reluctant reveal much about the device. In 2006, ONE News used the Official Information Act itself to reveal that three officers were injured during Taser training.

Anti-Taser campaigners tried to use freedom of information laws to ask for detailed descriptions from officers using Tasers during the trial and for their supervisors' assessments of their use.

However, police denied that request.

Now the ombudsman says that material should be released and the refusal to do so lacks accountability.

Wakeham says the Taser issue is of major importance to all New Zealanders given that the decision will be made without parliamentary oversight, Cabinet approval or sign-off from the Minister of Police, Annette King.

The decision on whether to introduce the devices - which have already been purchased at a cost of $50,000 - rests solely with the Police Commissioner as it is an operational concern rather than governmental.

"What needs to happen is that the government needs to step in and say 'hey, you cannot treat our citizens in this way'. Lives are potentially at stake and are at stake, we've seen in recent months fatalities overseas," says Council for Civil Liberties chairman Bott.

However, the ombudsman only has the power to recommend and the decision on whether to release the information rests with the police.