Theresa Soper has been running organised parties for teenagers. (Video first published in October 2017)

A mother has hosted a series of underage parties in a barn with up to 400 teens, some drinking alcohol and smoking drugs.

Her latest party, celebrating Halloween, ended about 9.30pm on Saturday when the police riot squad arrived and dispersed about 200 teens from the property.

Christchurch woman Theresa Soper says she has hosted about 18 parties over the last two years.

JOHN KIRK-ANDERSON/STUFF Up to 400 teens attend the parties.

The parties host up to 400 teens, some as young as 16, from across the city. Soper claims some of the partygoers are children of "very powerful people".

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Soper had worried about her 16-year-old daughter going to out-of-control parties with no security, so decided to host her own events where teens could party safely.

JOHN KIRK-ANDERSON/STUFF Twelve security guards named 'Guardians of the Doof' patrol the parties.

"What was happening is the kids have been going to parties – they vomit on the street, they pi.. off the neighbours and this is where they get in trouble."

The barn, named the Belfast Barn Bar, is on Main North Rd, near Marshland Rd. There are no neighbours in sight.

Soper said she initially paid for the parties herself at a cost of about $3500 each. No longer in a financial position to host them for free, she now charges $15 a ticket to cover costs. All the profits went to teen charities, she said.

JOHN KIRK-ANDERSON/STUFF The entrance to the barn.

The parties are organised by Soper and a group of 12 teenagers from various groups around the city who have had parties shutdown.

"They were so happy with a safe, controlled set up like this."

Soper gave Stuff a tour of the barn on Monday. Inside is a stripper's pole, a DJ booth, a wooden dance floor and some seats from the Ngaio Marsh Theatre.

Outside is a custom-made urinal labelled "pisser", some lockers for partygoers' bags and a barbecue.

There is also a time out room that can be used as a first aid room if someone has had too much to drink.

Soper said she did not supply alcohol, but teens brought it in with them. Soper said she had a strict rule of no straight alcohol and no bottles allowed. Bags were checked at the entrance.

JOHN KIRK-ANDERSON/STUFF Party organiser Theresa Soper says she's hosted about 18 parties in the last two years.

"There would be 60 per cent that do not drink at all and others just bring a few lolly waters (pre-mix alcohol)."

The parties are advertised on a Facebook page, which has since been closed down.

A post shown to Stuff listed seven rules for potential partygoers, including no weapons, no fighting and to leave when asked.

JOHN KIRK-ANDERSON/STUFF Theresa Soper says she's providing a "safe, controlled" place for teens to party at.

"Thanks for respecting do drugs get drunk and have a f…… time (sic)."

Soper said the post, made by her daughter, was supposed to say "don't do drugs".

"I am sure there is the odd few who have marijuana," Soper said. At a recent party, the security team of 12, nicknamed The Guardians of Doof, found a group of boys smoking a joint in the time-out room.

Earlier this month, Soper's daughter wrote on Facebook that she was thinking about hosting parties at the barn every weekend.

"This includes good sounds water barbecue and absolutely no pigs or noise control.

"You won't be paying hefty entries for it to be shut down after 5 minutes. Safe Safe and secure place with security and a good ol environment (sic)."

Soper said the teens just wanted to dance and party in a safe environment. She said any concerned parents were welcome to come have a look through.

"We want to get it right and would appreciate any ideas or help."

Senior Sergeant Gordon Spite, of the Alcohol Harm Reduction Unit, said police would consider what course of action to take once they believed they had a good understanding of all the circumstances.

He said the Sale and Supply of Alcohol Act introduced the concept of responsibly supplying alcohol to minors.

"Amongst a number of conditions it talks about the nature of the event. It is questionable whether, for example, several hundred minors all drinking together in a pseudo-licensed like setting could be described as responsible supply."

Spite said large events involving the consumption of alcohol were required to have a licence in most cases. Anyone could apply for one.

"Obviously this is to ensure that the event runs lawfully and safely and there are right systems and staff in place to see that that happens."