New Zealand's silver fern emblem is at the centre of a battle between the government and the International Rugby Board that has thrown the World Cup's volunteer programme into disarray.

Rugby World Cup Minister Murray McCully is insisting the silver fern be added to the volunteers' uniforms, with the IRB's logo.

But the IRB is resisting because of the fern's strong association with the All Blacks and the bias this would create if it were worn by the thousands of New Zealanders expected to volunteer.

It is understood the IRB also feels the fern is not consistent with the "look and feel" of the already-decided tournament branding.

The volunteer programme is a vital part of the government's plan for "a nation of four million hosts".

But the dispute has split it into two competing programmes.

The first is for the IRB-sanctioned volunteers, who will have access to venues and teams and be supplied with official T-shirts, jackets and tracksuit pants.

The second is being run by the Government's new NZ2011 office, which is organising the festival associated with the World Cup tournament and needs volunteers for a wide range of tasks outside the venues such as giving tourists directions at airports.

The IRB's involvement in the volunteer programme is viewed as crucial because branded uniforms are worn like a badge of honour by volunteers.

Mr McCully said he believed the "spirit of co-operation" would result in a joint volunteer programme - but the silver fern was non-negotiable, as it was an opportunity for New Zealand to promote itself to the world.

"That is the government's position and the IRB is in no doubt of that."

He said New Zealanders were investing $300 million in the tournament "and we just want to make sure New Zealanders can feel proud of the way their money is being spent".

Mr McCully accepted it would not look like good hosting to have "volunteering undertaken by people with All Black jerseys with a silver fern on them".

But there were "many ways to recreate the fern" so it would not look as partisan, and the NZ2011 office was working on designs.

The IRB's brand includes a stylised Maori design of a mangapore (hammerhead shark) and a rugby-ball-shaped koru, as well as its own logo.

Asked if that brand would look cluttered with the addition of a silver fern, Mr McCully said: "It is not unusual for two brands to live together."

The IRB declined to comment yesterday.

Labour's Rugby World Cup spokesman, Trevor Mallard, said the IRB was right to feel "ambushed" by Mr McCully's demand over the silver fern.

"This is a massive breach of faith by the Government," he said, "and totally undermines the united New Zealand approach to the Cup."