Tensions ran high on Saturday as the right-wing National Front group came to blows with the Multicultural Aotearoa group in Wellington.

Police called in extra staff to try and keep the two groups apart, but they couldn't stop the tension boiling over.

National Front members met at parliament at 10.30am, police said.

National Front director Kyle Chapman said earlier in the day he expected about 150 supporters to rally in favour of free speech and keeping New Zealand's current flag.

Multicultural Aotearoa, a group formed in response to recent racist activity in Wellington, gathered at Te Papa on the capital's waterfront at midday and marched to parliament.

However, despite police efforts to keep the peace, running skirmishes broke out around downtown Wellington and it took police nearly an hour to gain control.

At one stage, the outnumbered National Front were chased from the railway station and around parliament buildings by a group who called themselves the "scary fairies."

Chapman said the police handled the clashes badly and they should have used more force.

Chapman said mob mentality took over and police kept moving his group on instead of dispersing their opponents, who were threatening, pushing and throwing things.