The police union believes exempting Victorians under 18 from being charged for breaching bail sends the wrong message.
The Bail Act change, which came into effect on Monday, exempts children from being charged with breaching bail - an offence that can be punishable by three months imprisonment for adults.
Police Association of Victoria secretary Ron Iddles said there should be consequences regardless of whether the offender is under 18 or not.
"This sends a message to those who are under 18 that they can have total disregard for the law and there will be no consequences for your actions," Mr Iddles told reporters.
He said it would increase police workloads because they have to arrest the youths and take them to court - where they will most likely get bail again.
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Attorney-General Martin Pakula disputed claims the changes would weaken the justice system, or encourage a lack of respect for the law.
"If a child does breach a condition of bail, police still have the power to arrest them and bring them before a magistrate to have their bail reconsidered and that bail can still be cancelled," he told AAP.
But the opposition says the changes threaten community safety and means serious and potentially violent teens will be free to roam the streets while awaiting a court date.
"The changes will force Victoria Police to pursue more young criminals by summons which means they will automatically be free in the community while they await trial," opposition spokesman John Pesutto said.
He said senior police have voiced serious concerns about young criminals repeatedly breaching their bail and reoffending.
Committing an indictable offence on bail will continue to apply to children who commit crimes while on bail.
