A magistrate has expressed concern about the new bail laws, dubbing them the "Ray Hadley bail act" and saying they haven't been thought through.

The new laws, which passed through the NSW Parliament in September, require adults accused of certain offences to "show cause" as to why their detention before trial is not justified.

Ray Hadley, who ran a campaign against the previous bail laws. Credit:Peter Rae

That applies to people charged with "serious offences", including those that carry a life sentence, those committed while on bail or parole, involve the sexual assault of a child, or repeat acts of personal violence.

The government described the changes as a "toughening up" of previous laws introduced in May, under which a presumption against bail for serious offences, such as murder, was replaced with a broad consideration of whether the accused posed an "unacceptable risk" of reoffending.