Parents will need to take more responsibility for their teenager's alcohol consumption, with a text, phone call or note of consent set to be a requirement under changes to liquor legislation.
The Alcohol Reform Bill is set to have its committee stage next month, with the government planning to introduce several changes with a supplementary order paper, before the bill's third and final reading.
Justice Minister Judith Collins on Tuesday announced the proposed changes will include amendments recommended by the justice and electoral committee in August last year.
She is yet to make the supplementary order paper public, but says the major change is increasing parental responsibility for young people's drinking.
"If someone wants to supply alcohol to under 18-year-olds, they need to get the express consent - that might be a text or it might be a phone call, or it might be something else in writing, and if they don't then they're breaking the law," Ms Collins said.
Without consent, the person supplying the alcohol will face a fine of up to $2000.
"I think that's very important and I think many parents of teenagers are going to be very pleased that we're helping them."
MPs will have a conscience vote on splitting the alcohol purchase age during the committee stage.
The bill proposes keeping the purchase age at 18 at on-licence venues, such as restaurants and bars, and raising it to 20 at off-licence retailers, like liquor stores and supermarkets.
Lobby group Family First wants the purchase age raised to 20 for both on- and off-licences.
Opposition parties are critical of the government's timing with the announcement of changes to the bill.