It sounds like bliss: an online invite to live in an island idyll. But, finds Nick Squires, these castaways have had to weather a cyclone, a fire and � worst of all � internet scepticism

It adds a tech-savvy, 21st century twist to the image of the South Seas as an untouched tropical Eden. More than 200 years after the fantasy was first fostered by British and French naval explorers, an idyllic island in Fiji has been settled by a modern-day "eco-tribe".

Described as a bold social experiment, "Tribewanted" combines elements of Robinson Crusoe, Lost and the reality TV show Survivor - but not, as yet, Lord Of The Flies.

Founded by a young British entrepreneur, the idea is to recruit 5000 tribe members via the internet.

A maximum of 30 are allowed to live on the island at any one time, with the rest casting online votes from their homes or offices on decisions such as whether to opt for a wind, solar or bio-diesel generator.

It is 10 months since the first batch of intrepid castaways waded ashore on Vorovoro island, in the untouched north of Fiji.

Since then they have had to contend with a series of potential disasters that not even the producers of a reality television show could have dreamed up, including internet scepticism, a fire, a military coup and a cyclone.

"The fire was unbelievable," said Tribewanted's creator, Englishman Ben Keene, who previously worked for a company managing gap year projects for young people.

"There was a big plume of black smoke over the island. I thought I was watching the whole dream literally go up in flames."

The fire struck in September, just a week after Keene, 27, and his international band of "First Footers" arrived on the mile-long island with the aim of creating a sustainable community in harmony with a real-life Fijian tribe.

The blaze was eventually put out, but not before coming perilously close to sweeping through the thatched huts they had begun to build.

It was a disconcerting start to an enterprise which excited international interest when it was first launched in April 2006.

Tribewanted is part business venture, part MySpace-style online social network and part desert island fantasy.

So far, 1200 people from more than 20 countries have joined up to the project. Around 200 have spent time on the island, from 18-year-old French backpackers to 60-something teachers from the US.

For £180 a week, for a maximum of 12 weeks, participants are entitled to live on Vorovoro, one of Fiji's 333 islands, which Keene found after a worldwide search.

The regular turnover of participants should prevent the development of cliques and personal feuds, Keene said when the project was launched last year, and so far he appears to have been proved right.

The fire was one of a succession of potential disasters which threatened to extinguish his green dream.

Two months after the launch, an American blogger decided that the enterprise was an elaborate scam.

Within days of his blog being posted on the internet, the hundreds of people who had been signing up suddenly dwindled to a trickle.

"It nearly shut us down," said Keene, sitting on the beach beneath the shade of a palm tree. "If you typed Tribewanted into Google, the blog came up as the second item. This guy didn't interview us or even email us. But his allegations just made us more determined to make the whole thing work."

The next challenge came in December, when Fiji's government was ousted in a military coup and Britain, the US and other countries advised their citizens not to travel to the South Pacific nation.

A powerful cyclone then hit the island in February, toppling trees and destroying a jetty. Water has also been a problem - the island has no streams, so thousands of litres have had to be shipped in by barge from the mainland.

In true Survivor style, the tribe has weathered all these challenges and each week welcomes new arrivals, who come by boat after flying into the nearby island of Vanua Levu.

The "village" they encounter covers an area the size of a football pitch, with a beach to the front and a steep rocky ridge behind - beyond which lies a "secret beach", accessible only by rope.

There are composting toilets, open air bucket showers in a jungle glade and small plots planted with herbs and vegetables. Food scraps are turned into compost, rainwater is collected and empty plastic bottles are turned into guttering and pipes.

The dozen "tribeys" on the island last week cleared patches of jungle for pineapple plants and citrus trees.

"I always knew it would be an amazing experience, but I underestimated how much I'd learn about living more sustainably," said Anna Kemp, 25, of Troon, Ayrshire, who gave up her job as an equity analyst in London to come to Fiji.

"I'll take home with me lessons about the things you can manage without and about the conservation of resources," she said, covered in sweat and dust as she struggled with a giant pile of freshly cut grass. "It really makes you think about the footprint you leave on a place."

Vorovoro is owned by a local tribe and its chief, Tui Mali, had been contemplating leasing it to a developer or to the makers of Survivor, who ended up filming on a neighbouring island.

"If we had allowed a big hotel to be built here, there would be a line between the locals and the tourists," said the chief, illustrating the point by scraping a mark in the sand with his big toe. "With Tribewanted, this line has been rubbed out."

In addition to the £47,000 Keene paid for the lease of the island until 2009, the project has sparked among the islanders a renaissance of almost forgotten skills such as the construction of bures pronounced boo-ray, or timber huts.

It has also provided jobs for local people - the men work as boatmen and builders, while the women cook meals in a tin-roofed shack shaded by banana trees.

"The tribe has made us dig more deeply into our traditions," said Savenaca Matanawa, 32. "It's strengthening our old ways and making us appreciate our culture more."

The tribe and their Fijian hosts work together during the day and at night share coconut shells full of kava, a mildly intoxicating drink which looks like dirty washing up water and tastes like mud.

Creating a truly sustainable community has been hard. Few of the "tribeys" knew how to catch fish until the recent arrival of a Hawaiian, Ryan Garcia, 25, an experienced spear fishermen.

Undeterred by having a coral trout snatched from the tip of his harpoon by a pair of sharks, or by the menace of highly poisonous sea snakes, the former tour guide has been supplementing the tribe's diet with fresh fish.

"The idea of leaving a place better than when you found it is very un-American. Americans expect to be served when they go on vacation; here the emphasis is on giving something back," said Garcia.

Most food is bought in the mainland town of Labasa and brought by motor boats to the island three times a week, although that will change as the jungle gardens develop.

"At the moment we're producing too much waste and not enough food," said James Strawbridge, 23, the presenter of a BBC2 programme, It's Not Easy Being Green, who has been recruited as sustainability manager. "But there are a lot of good intentions and a genuine desire to change how things are done."

For cooking and lighting, the tribe relies on gas and kerosene, but there are plans to build a "green gym", in which rowing and bicycle machines will provide electricity.

The BBC will broadcast a five-part documentary on the project in the autumn, and Keene has just finished a book about the whole experience, to be published in the next few months.

He is aware of the contradiction of establishing an eco-project which requires tourists to take gas-guzzling long-haul flights from the other side of the world.

"But I think the way we educate people on the island, and the impact we can have online and through the media, hopefully outweighs our carbon footprint," he said.

When the lease on the island expires in 2009, Tui Mali will decide whether to continue with the project.

So far, he is pleased with the way the foreigners have breathed new life into Vorovoro, which was previously inhabited only seasonally by one or two families.

"We have joined together to build a big family," said the chief, downing another coconut shell of kava as the sun sets over the South Pacific. "All the world is coming to Vorovoro."