The mother of a 14-year-old girl hosted alcohol-fuelled parties for her daughter's friends that ended with under-age teens vomiting and passed out.

Bronwyn Tracey Saunders, 46, supplied alcohol to several teenagers her daughter invited to two parties held at their house late last year.

She was convicted and fined $2000 in the Christchurch District Court this month on six charges of supplying alcohol to minors after parents of the teenagers she bought alcohol for complained to police.

It is the first conviction for supplying alcohol to minors in Canterbury under new liquor laws that came into effect in December 2013.

Police said the conviction was not a direct reflection of the success of the new laws, as most cases of adults supplying alcohol to minors went undetected.

Saunders hosted two parties at her house attended by 20 to 30 of her daughter's friends and on both occasions accepted money from teenagers to buy them alcohol.

In November, her daughter set up a "Year 9 drinks" Facebook group chat and told her friends if any of them wanted alcohol, they needed to give her money and she would pass it on to her mother to buy it.

Saunders' daughter then met three of her male friends at Christchurch Boys' High School where they gave her money. Saunders gave them beer and cider at the party the next day.

According to police, several children at the party, including her daughter, were so intoxicated they were vomiting.

In December, her daughter met her friend again at his school gate, where he gave her money and asked for a box of beer.

A week later at another party hosted by Saunders, she gave him a box of beer. During the party, two year 10 girls asked Saunders to buy them alcohol and were driven to the shop, where she bought it for them.

Several girls were later "stumbling and slurring their words", one lay down in Saunders' daughter's room and began to vomit. Another partygoer placed her in the recovery position and took her to the shower.

Saunders did not ask for consent from the parent's children at either party.

After parents complained about the incidents, police spoke to Saunders, who admitted to purchasing alcohol for the three boys at the November party. She also admitted supplying alcohol to the unknown year 10 girls at the December party but denied supplying beer to the boy.

She said she had relied on her daughter to tell her all of the children had parental consent to drink. Saunders has previously appeared before the court.

When Fairfax Media visited Saunders' last known address, the new tenants said the landlord had told them Saunders had "done a runner".

Sergeant John Harris said convictions under the law were rare as they were "not necessarily drawn to police attention".

"It probably happens all the time and we're never made aware of it.

"We're dealing at the moment with another licensed premise who supplied alcohol to under aged people and it's more effective to have the premises suspended."

Police also tended to use a pre-charge warning or the community justice panel to deal with those found to have supplied alcohol to minors, as the offending was usually minor.

In this case, a conviction was necessary as Saunders' offending was not a one-off and was "on the upper end of the scale", Harris said.

Lucy Teari Winnie Snowden, 25, was convicted and fined on one charge of supplying alcohol to a minor in June 2014 after she gave a 9-year-old boy alcohol at a skate park. A video of the drunk boy was uploaded to YouTube.

In August, an 18-year-old Cromwell woman was convicted and fined on the same charges after supplying a bottle of vodka to a 16-year-old girl, who was later found unconscious and covered in vomit on a grass verge.

National addiction centre director Doug Sellman said the case was an "excellent signal to us all that this is a psychoactive drug and it's for adults only".

He said while the laws had become tighter, they had no evidence it would have an impact on alcohol-related harm.

"Our big problem right now is marketing. All these 14-year-olds are continuing to think it's cool to drink and it's cool to drink heavily," Sellman said.