The Law Society is describing a bill that could result in prison terms for some minor fineable offences as a step too far.
The Criminal Procedure Legislation Bill is intended to make small technical amendments to ensure legislative intent is made clear.
However the Law Society said the bill includes significant amendments that are going under the radar.
Law Society reform committee member Graeme Edgeler said some things that are legal at present or deemed very minor crimes could have much more serious consequences.
These include possessing computer software that can access someone else's computer with an intention to commit an offence.
Mr Edgeler said other changes will give community magistrates more power and government ministers the power to amend criminal legislation.
Parliament's Justice and Electoral Committee will report back on the bill on 4 June.
