Skinhead groups are on the rise again, a gang expert says, as a prominent skinhead yesterday admitted his role in the brutal killing of a Korean backpacker.

Shannon Brent Flewellen, 30, of Nelson, admitted in the High Court at Christchurch that he choked and stomped on the neck of Jae Hyeon Kim after he and white supremacist Hayden McKenzie had picked up the man hitch-hiking on the West Coast in 2003.

Flewellen had been due to go to trial in a few weeks.

Police say that as Flewellen put his arm around Mr Kim's neck to choke him, McKenzie had given the instruction "no blood" in German.

Flewellen is still to be sentenced, but McKenzie is already serving a jail term of at least 21 years for the murder of the 25-year-old. That sentence was imposed while McKenzie was already in jail for the 1999 killing of gay cross-dresser James "Janis" Bambrough.

Canterbury University researcher Jarrod Gilbert, who has been given rare access to the inner workings of some gangs, said skinhead groups had been most active in New Zealand during the 1990s, and many had petered out. Among these was the feared Fourth Reich, of which McKenzie had been a member.

But Mr Gilbert said there had been a "quite significant" resurgence in skinhead gangs in the past two years.

"[That trend] I can really only link to the fact that the economy starts to bite hard and that's allowed for predominantly young Pakeha to be dissatisfied, and form together under something they can believe in and hold on to."

Using a white supremacy rallying call, these mostly unsophisticated groups were forming throughout the country, but the strongholds tended to be in the South Island.

But groups were forming at least as far north as Hamilton, he said.

People such as Flewellen and McKenzie could be seen as role models to young wannabes because they "walk the walk", Mr Gilbert said.

Flewellen yesterday admitted being in a car with McKenzie and another man when they picked up Mr Kim as he tried to hitch a ride from Westport some time between September 29 and October 22, 2003.

When McKenzie later stopped the car, he made out that it was stuck and the occupants, including Mr Kim, were asked to get out and push.

Flewellen grabbed Mr Kim from behind in a choke hold, while McKenzie gave the "no blood" instruction and helped to restrain the Korean.

Mr Kim eventually collapsed to the ground. Flewellen then stomped on his neck area with his heavy boots and stood on his throat to ensure he was dead. The tourist was later buried.

Mr Kim was reported missing in 2004, but the case went cold until 2008 when McKenzie led police to his grave.

Mr Kim's family were to be told of Flewellen's guilty plea via the Korean consulate. The Crown will seek a minimum prison term when he is sentenced this month.