Dame Sian Elias' objections ' />

The Chief Justice has made a stinging criticism of the Government's sweeping reforms of the criminal justice system.

Dame Sian Elias' objections - revealed in a submission to Parliament's justice and electoral committee - place the Government and the judiciary firmly at loggerheads.

Dame Sian said the proposed changes were being made too quickly and threatened a defendant's long-standing right not to help the prosecution.

The reforms are in the Criminal Procedure (Reform and Modernisation) Bill, which is before the committee.

The bill would, among other things, require lawyers of the accused to disclose their defences - including any issues in dispute - to the prosecution in advance of a trial.

Failure to do so would mean the judge or jury could take an adverse view of the defendant, and it could also lead to sanctions against the accused and their lawyers.

Dame Sian said she had "grave concerns" the provisions were "contrary to longstanding principle, being inconsistent with a defendant's right" not to volunteer information that might help the prosecution.

"I appreciate that some defendants and counsel are guilty of abusing the system but, on balance, the judiciary is not persuaded that this provides good reason for the departure from basic principle, which is involved in any requirement for advance disclosure of an intended defence," she said in her submission.

Sanctions would also be ineffective and impractical because of "uncertainty about whether the abuse of the system is the fault of the defendant or of counsel", she said.

Dame Sian also objected to the speed with which the bill, which signals significant changes, was being progressed.

"It has been a matter of concern that the reform has been developed under such tight time constraints."

The bill's provisions about pre-trial procedures still had many gaps, and "in the present state of the bill, it is impossible adequately to address the many issues arising".

The bill would also change the threshold for electing a jury trial - from offences carrying a maximum sentence of three months to three years - and change the rules for name suppression.

Dame Sian's submission was made in consultation with the president of the Court of Appeal, Justice Mark O'Regan, and Chief High Court Judge Helen Winkelmann, representing the "view of the judiciary".

The New Zealand Law Society and criminal lawyers have also strongly criticised the bill, though many also believe some reform is necessary.

District Court judges have also made a joint submission to the committee, saying the pre-trial requirements empower the prosecution with "an unprecedented opportunity to refine its case in the light of issues it may not have considered".

The submission does not take a stance on whether this would be a good or a bad thing.

The committee is due to report back by the end of May.

It is not the first time Dame Sian has taken aim at the Government. In a 2009 speech she criticised the punitive approach to the criminal justice system and suggested granting amnesty to some prisoners to relieve New Zealand's bulging prisons.