New Zealanders stand to lose some hard-won freedoms under a bill moving largely under the radar through Parliament.

The Search and Surveillance Bill will remove an important civil liberty and expand state liberties for authorities ranging from the police to the Department of Internal Affairs.

The right to silence will fall to a new coercive power, the examination order, forcing people alleged to have knowledge of fraud or organised crime to talk to the police.

Another innovation, the production order, allows police to demand that innocent individuals or organisations hand over materials that might or might not relate to an offence carrying penalties of five or seven years' minimum jail.

Failure to comply would automatically attract a penalty of up to $40,000 or imprisonment.

And the bill gives authorities an invitation to force the news media to reveal confidential sources, threatening the public airing of some of the country's most important, and uncomfortable, news stories.

The bill provoked criticism from the Law Society and human rights and civil liberties advocates. It has been revised after two rounds of select committee consultation. Yet its shift of rights from the citizen to investigating authorities remains.

Agencies of state want greater powers to uncover and prosecute complex financial, drug and organised crime. The changes are couched in terms of convenience: production orders will mean organisations can provide material to the police without a messy police search of their premises, and examination orders will give reluctant lawyers, accountants and the like an ethics-free pass to tell on their clients.

No changes this important should be made simply to make the state's job easier. Any assumption that authorities know best and the innocent have nothing to fear have a fug of authoritarianism about them. They sit poorly with a Justice Minister and Government nominally in favour of the rights of the individual.

The threat to media freedom is made clear by the misuse of such powers by the Serious Fraud Office in demanding information from the National Business Review newspaper.

Until now, the SFO has alone had access to such orders. It is, sadly, a model for the more limited but worrying extensions being offered the police and others. In harassing the NBR, the fraud office exposed its own failings and the failings of such instruments.

There is a danger that the media's right to protect confidential sources - a privilege recognised in the Evidence Act 2006 and qualified only by a judge's decision that public interest might outweigh confidentiality - will be subverted by police access to examination and production orders.

Search warrants cannot make individuals talk. Once any agency has new powers it inevitably deploys them to save itself time or scrutiny.

That matters for the public. Important revelations of wrongdoing by criminals, business or political leaders and, crucially, investigating authorities themselves are invariably from confidential sources.

News is, by one definition, something that someone, somewhere, does not want made public.

While media organisations will invariably refuse to reveal their sources and face punishment, the increased perception that confidentiality is at risk will cause whistle-blowing to dry up. The truth will not get out, and the public will lose its right to know.

Streamlining search laws cannot justify removing the right to silence and circumventing media protection of confidential sources.

Parliament should excise the bill's illiberal over-reach, keeping the target squarely on wrongdoers, making orders subject in advance to a fair hearing and exempting the media from their auspices.