Police are rejecting claims they were heavy-handed in dispersing about 200 young partygoers on the Kapiti Coast.

Criticism has come from those at the birthday party and others around the Rimu Rd, Kapiti Lights area on Saturday night when the Wellington Public Safety Unit used batons against the party goers.

The 18th-birthday party was posted on Facebook and attracted teens from Otaki to Porirua. Bottles, rocks and shopping trolleys were hurled at police, who systematically dispersed groups of partygoers through the streets.

Aaron Bloodworth, 18, was one of those marched through the town by police.

"Police blew the whole situation out of proportion . . . there were well over 200 people marched down Rimu Rd," he said. "I don't know what they were expecting, having the full-on riot police there.

"A large bunch of excitable, drunk youths would see that as an opportunity to go crazy, as was happening down Rimu Rd and through Coastlands."

The mother of a 17-year-old who went to the party, said her son suffered extensive bruising when he was "unnecessarily set upon by two police officers with batons and a third joined in".

"I understand the police being tough with those who deserve it, but on this occasion, they were out of line."

Mikaere Kopeke said she was waiting in line at Paraparaumu McDonald's with friends when about five police officers armed with batons approached them.

"They were yelling ‘F... off' and ‘Get the f... out of here' when we were simply waiting to collect our food. After trying to talk to them about collecting our meal they began pushing and shoving us out of the area, with some of us ending up on the ground," Ms Kopeke said.

A 20-year-old woman, her partner and a friend were calling a taxi outside a bar in Kapiti Lights when they became embroiled in the clash.

"They [police] beat the shit out of the three of us even though we had nothing to do with the bottle-throwing; the force the police used was disgusting," she said.

She suffered a large cut to her leg when she was forced to the ground and dragged along the road, she said.

Kapiti-Mana area commander Inspector John Price did not believe the police overreacted.

"I do not believe the police were heavy-handed at all. When our guys arrived [at the party] there was a situation of 170 mostly drunken people and it was considered to be out of hand. The Public Safety Unit from Wellington were called to assist.

"There were missiles - bottles - thrown at police staff. The behaviour of those who attended [the party] was disappointing and police carried out actions to disperse the numbers," Mr Price said.

He advised people holding parties to ensure precautions were taken to ensure only those invited attended. "Those who are not invited and not welcome are the ones that cause the problems."

- © Fairfax NZ News