A placard-waving National supporter claims the right to free speech has been shut down, after being accosted at a Labour Party rally in Christchurch.

Labour leader Jacinda Ardern was cheered repeatedly by a large crowd of supporters during a visit to the University of Canterbury on Thursday. It was part a four-hour whistle stop trip to Christchurch – just long enough to visit Meadow Mushrooms – after an invitation from former National minister Philip Burdon, whose family own the business.

Ten minutes after Ardern had moved on from the James Hight building, a National-supporting student, Jacob Butson, moved into the rally with a blue sign reading "Vote National".

IAIN MCGREGOR/STUFF Young Nat Jacob Butson gets manhandled at a Labour Party rally at Christchurch's University of Canterbury.

When asked where the Young Nats at the rally were, Butson replied he was the only one.

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"I'm the Young Nats. I'm surrounded by lefties, but I'm proud enough to show my support for the National Party."

IAIN MCGREGOR/STUFF A man wearing a yellow hi-vis vest appeared and attempted to rip the sign off Butson.

Soon after, a man wearing a yellow hi-vis vest appeared and attempted to rip the sign off Butson. The man implied that he was working at the university campus.

"It's my job here. I'm trying to do my job here. He's just trying to cause trouble," the man said.

Butson tried to stop him and asked why the Labour supporters were allowed to have signs and he wasn't.

IAIN MCGREGOR/STUFF Butson says all party supporters should have the right to express their opinions on campus.

"You should respect my right to say something," Butson said.

The man said Butson had no right to be there because the crowd was mainly Labour supporters.

"Who here is National?" the man asked the crowd. The crowd answered with a small cheer.

The man then tried to wrest the sign from Butson again and succeeded, then threw it into the crowd hitting a young woman on the head. She appeared unhurt. Butson then retrieved the sign.

Butson said all party supporters should have the right to express their opinions on campus.

"That's what the left do, they villainise us because we have a different opinion. I'm not ripping the signs off the Labour people, I respect their right to..."

At that point, Butson was interrupted by Labour supporters.

The hi-vis man moved on before he could be interviewed by Stuff.

A University of Canterbury spokeswoman said they did not know who the individual was. A photo has been sent to the university for verification.

There was no ban on National supporters on campus, the spokeswoman said.

Max Farra, the former president of the university's queer society QCanterbury, said this week he felt forced to resign as president because of his allegiance to National.

Farra​, 20, stirred controversy when a Young Nats promotional social media post showing him pledging his support to the party was shared with QCanterbury members.

The club rejected Farra's claim he was ousted because of his political views.

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