In 1953 a lahar -- Indonesian for a volcano-related mudslide -- swept down from Mount Ruapehus crater lake taking out a main line railway bridge just before an overnight express passed by. The train plunged into the torrent, killing 151 people.

Ruapehu now has a bigger lahar building up in the fragile crater lake, and critics claim the government is not going to act for fear of offending the indigenous Maori people who believe the mountain is sacred.

Mount Ruapehu ("exploding pit") is one of three active volcanoes in the World Heritage-listed Tongariro National Park, a little populated landscape in the middle of the North Island, 300 kilometres (186 miles) south of Auckland.

Te Heuheu Tukino, chief of the Tuwharetoa people, gifted the park to the nation in 1887.

In 1995 and 1996 Ruapehu, 2,797 metres (9,230 feet) above sea level, erupted in spectacular fashion, sending a plume of ash over parts of the North Island, wrecked the ski season but otherwise did no other damage.

When it finished the crater lake began refilling, supported only by mud and volcanic ash walls which the Department of Conservation estimates will give way sometime in the next three years.

The department says when the ash sweeps down the Whangaehu Valley on the south side of the mountain the lahar will be up to 30 percent greater than in

Rail and road bridges have been strengthened and warning sensors set up on the dam and down Whangaehu.

In January Opposition Leader Don Brash said the government was giving race-based preference to Maori who make up 14 percent of the four million population.

The speech was credited with giving his National Party a sudden surge in opinion polls, overtaking the government of Prime Minister Helen Clark.

Brash accused the government of kowtowing to Maori: "We refuse to undertake potentially life-saving earthworks on Mount Ruapehu lest we interfere with the spirit of the mountain".

Last week one of his party colleagues, Nick Smith, said a government decision to do nothing was madness and it was only acting out of political correctness toward Maori.

"These works would cost just 200,000 NZ dollars (126,800 US) and would remove the very serious risk to life and millions of dollars in damage to properties downstream...

"This latest justification for inaction is a smokescreen for the real reason of not wanting to offend Maori or environmentalists."

Conservation Minister Chris Carter said the government had considered intervening to stop the lahar, but decided instead to bolster the extensive safety measures already in place around Ruapehu.

"The options for attempting to prevent the lahar are either impractical, unsafe or likely to make the problem of lahars on Ruapehu worse in the future."

Carter said there was a greater chance of people being hurt while trying to carry out intervention work than there was in allowing the lahar to occur naturally.

Federated Mountain Clubs president John Wilson welcomed the government's position.

"New Zealand has set aside the volcanoes of Tongariro National Park as a special place where natural processes are left to take their course," he said.

He said people should plan to minimise risks from volcanic activity and other natural events and "should not linger in the Whangaehu Valley, but cross it as quickly as possible to higher ground."

TERRA.WIRE