Prime Minister John Key has called the chaotic aftermath of Undie 500 rally in Dunedin "madness", saying some of the alleged rioters had blighted their lives.
Up to 80 people were arrested while police dispersed mobs of around 600 drunken students gathering on Saturday and Sunday nights on Castle St.
Some students were likely to graduate with criminal convictions, which was a "waste of their futures", Mr Key said.
"They have had plenty of warning. This is just a sort of organised chaos down there," he told TVNZ's Breakfast programme.
The annual event, organised by Canterbury University engineering students, involves a pub crawl from Christchurch to Dunedin, in cars worth under $500.
About 90 percent of those arrested were Otago University students.
Those participating in the event were warned by police diversion would be opposed in court, and Mr Key agreed with that stance.
Advice from Police Minister Judith Collins was students "laced up" after watching the Tri-Nations rugby test came out "spoiling for a fight", he said.
Dunedin police slammed the arrogance of Canterbury student leaders following the rally.
Members of the mob pelted police with bottles, bricks and bicycle parts and burned furniture on the street, Inspector Dave Campbell said.
"I think the Canterbury student leaders are showing arrogance and selfishness. We've told them they aren't welcome, the mayor's told them they aren't welcome, but they insist on coming," he told Radio New Zealand.
Police responded, at one stage running out of pepper spray and having to get more to subdue the drunken young people.
"Fortunately, we still had another carton (of pepper spray) back at the station, so we got that to the front line troops and kept on using it." The violence was simply a result of a large group of young people getting drunk who had nothing better to do, he said.
"We thought it would be better this year, with the blanket no-diversion policy and the North Dunedin-wide alcohol ban and the publicity we'd put through the student's Critic magazine. We were really hopeful behaviour would be improved."
Mr Campbell said part of the problem was the expectation surrounding the event, with some Otago students feeling they needed to "show off".
Those arrested would appear in Dunedin District Court this week.
Dunedin Mayor Peter Chin, a strong opponent of the rally coming to his city, hoped police would "walk the talk" when prosecuting those arrested.
"If a few potential careers are wrecked, so be it," he said.
"There may be some parents out there that are going to be to be feeling very sorry for themselves and their children."
