Victoria's opposition wants drug-using accused killers to give up the names of their dealers because it is "fair and proper" under a plan to hold suppliers responsible for mass-casualty attacks.
Dealers who sell drugs to addicts that go on to kill people, and know their buyer could turn violent, could be charged and face 10 years' mandatory jail under a proposal announced by Opposition Leader Matthew Guy on Thursday.
"I'm guilty of having a policy, it's a good one and I'm going to enforce it," Mr Guy told reporters on Thursday.
However, the laws would be heavily reliant on accused criminals giving up the name of their dealer to police, shadow attorney-general John Pesutto said.
"If the accused who appears in court wants to say that they are affected by ice ... it will be on them to disclose the identity of their dealer," he said.
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"It's only fair and proper that they should reveal the identity of the person who supplied them with the ice."
Mr Guy and Mr Pesutto said there would be other means of identifying dealers, such as through chemical analysis, but admitted the burden of evidence will be high.
"We recognise there will be challenges but that isn't a reason to do nothing," Mr Pesutto added.
Ice use is suspected of being linked to January's fatal Bourke Street car rampage and last week's Flinders Street car attack that hospitalised 18 pedestrians.
