The bus, a Stray Travel coach, left the road about 30km south of Westport about 3.50pm on Saturday and tumbled 10m down a bank.

One woman, a 62-year-old British national who lived in Spain, was thrown from the bus and killed instantly, police said.

The crash is the latest in a series of accidents involving tour buses and has generated negative publicity for New Zealand's tourism industry in some of its core markets, including in Britain.

National Party transport spokes man Maurice Williamson said he would be asking questions in Parliament about the safety of tourist bus operations.

A Dutch passenger, who declined to be named, said the bus ``just drove off the road''.

``I heard someone shout to keep right. I looked up and I thought he (the driver) would steer it back to the road but that didn't happen.

``We flipped over once, throwing us all around, before the bus landed on its side, more or less. It was like being in a tumble dryer.''

When the bus settled, 15 passengers helped one another out through a skylight, and scrambled 10m up the bank to the road.

A passing motorist travelled the 3km to Charleston and raised the alarm because there was no mobile phone reception at the crash site.

A 27-year-old British woman remained trapped in the bus and had to be cut free by emergency services.

Westport fire chief Pat O'Dea said firefighters smashed one of the large windows then used the jaws of life to cut the woman out.

She was airlifted to Grey Base Hospital with neck and shoulder injuries and requested her condition not be released to the media, although the police said last night that her condition was improving.

Firefighters then helped retrieve the body of the dead woman.

Her name has not been released at the request of her next of kin.

Three other passengers were taken to Westport by ambulance where the other passengers later met and stayed the night in a motel.

A Grey Hospital spokesman said ``four or five others'' were seen at Buller Hospital but were discharged, while the majority were unharmed.

The driver of the bus, a 36-year-old man, suffered minor injuries but the Dutch tourist said he was ``mentally, really shaken-up''.

The driver was being questioned by police.

Stray Travel said the driver was experienced. He had been with the company for three years.

O'Dea said the bus appeared to have moved off the tarseal where the road edge collapsed, sending the bus down the embankment.

The road was ``not a dangerous piece of road, in my opinion'', he said.

The Nelson Serious Crash Unit and the Commercial Vehicle Investigation Unit from Christchurch were investigating the accident.

News of the crash was picked up by several international media outlets, particularly in Britain.

The BBC website had spoken to the parent of a woman on the bus.

Amy Lewis, 23, told her father, David Lewis, in Wales that she had been sitting next to the woman who died.

The woman had stood up moments before the crash to move to the front of the bus, she said.

London's The Times ran a report that concluded with a list of New Zealand tourist bus crashes, including three on the West Coast alone.

Already this year there have been three incidents with tourist buses in the South Island, including a bus that caught fire near the Homer Tunnel on the Milford Road and a fatal accident on the same road between a tour bus and a mini-van in January.

Two tourists were seriously injured and 40 others were hurt when their Kiwi Experience bus crashed down a bank on the West Coast last year.

Bus and Coach Association president Craig Worth said it ``wasn't a good look'' but he thought there were adequate licensing controls on coach drivers.

Williamson said he would be putting questions to the Minister of Transport Safety in Parliament to check whether New Zealand was ``out of kilter'' with other countries for tourist bus crashes.

``One thing we don't want to get as a nation is a bad reputation. It would be dreadful for us as an economy.''

Tourism Minister, and Labour member for West Coast-Tasman, Damien O'Connor said he was ``absolutely happy'' with safety measures in the tourist bus industry.

``For the number of people trans ported and the number of roads, we have the highest levels of safety.''

The responses by emergency crews showed New Zealand also had excellent support services, he said.

The country needed to keep stan dards high and that could include ``spending more on roads''