PEOPLE in NSW will no longer have the "right to silence" when being questioned by police after the Shooters and Fishers Party voted with the government on its bid to combat gang violence.

Critics of the laws - which the government will now push through the lower house - say it's a fundamental attack on people's rights.

Greens MP David Shoebridge wants the government to come clean on the deal it struck with MPs from the minor party to get the laws through the upper house, where they have the balance of power.

"The question is, what have they been offered in return?" he told AAP.

The legislative changes allow judges and juries to take a negative view of people who exercise their right to remain silent.

The government flagged the move last August following a spate of drive-by shootings in Sydney's west.

Under the new laws, an unfavourable inference can be drawn if an accused person fails to mention something during official police questioning that they could reasonably be expected to mention, and that they later rely on in their defence.

During debate in the upper house on Wednesday, Labor MP Sophie Cotsis said it was "wrong in principle and undesirable in practice".

Mr Shoebridge said it was hard to imagine a more fundamental attack on the basic workings of the criminal justice system "under the guise of dealing with bikies and making trials more efficient".

"The people who will be most affected by these changes will be the most marginal," he said.

"The right to silence is not simply a right that criminals choose ... it's a right all of us should have under questioning by police."

The bill was expected to be opposed by the Greens, Labor and the Shooters and Fishers Party but it ended up being passed 21 votes to 19.

Asked earlier in the day if he had spoken to the Shooters and Fishers Party, Mr O'Farrell replied, "I am simply expecting them to respect the powers the police wanted, powers that could assist in tackling gun crime across western Sydney".

NSW Police Commissioner Andrew Scipione denied the legislation would infringe on a person's basic rights.

"This is simply a matter of trying to level the playing field," he told reporters in Sydney.

"This is about making sure that people can't concoct an excuse when they get to court on the first occasion and try and catch us out by not having disclosed that previously.

"I don't think it trashes civil liberties."

Opposition Leader John Robertson called the proposal a "government stunt" and said if Mr O'Farrell was serious about gun crime he would outlaw bikie gangs.