The trouble started when Raj Patel appeared on American TV to plug his latest book, an analysis of the financial crisis called The Value of Nothing.

The London-born author, 37, thought his slot on comedy talkshow The Colbert Report went well enough: the host made a few jokes, Patel talked a little about his work and then, job done, he went back to his home in San Francisco.

Shortly afterwards, however, things took a strange turn. Over the course of a couple of days, cryptic messages started filling his inbox.

"I started getting emails saying 'have you heard of Benjamin Creme?' and 'are you the world teacher?'" he said. "Then all of a sudden it wasn't just random internet folk, but also friends saying, 'Have you seen this?'"

What he had written off as gobbledygook suddenly turned into something altogether more bizarre: he was being lauded by members of an obscure religious group who had decided that Patel – a food activist who grew up in a corner shop in Golders Green in north-west London – was, in fact, the messiah.

Their reasoning? Patel's background and work coincidentally matched a series of prophecies made by an 87-year-old Scottish mystic called Benjamin Creme, the leader of a little-known religious group known as Share International. Because he matched the profile, hundreds of people around the world believed that Patel was the living embodiment of a figure they called Maitreya, the Christ or "the world teacher".

His job? To save the world, and everyone on it.

"It was just really weird," he said. "Clearly a case of mistaken identity and clearly a case of people on the internet getting things wrong."

What started as an oddity kept snowballing until suddenly, in the middle of his book tour and awaiting the arrival of his first child, Patel was inundated by questions, messages of support and even threats. The influx was so heavy, in fact, that he put up a statement on his website referencing Monty Python's Life of Brian and categorically stating that he was not Maitreya.

Instead of settling the issue, however, his denial merely fanned the flames for some believers. In a twist ripped straight from the script of the comedy classic, they said that this disavowal, too, had been prophesied. It seemed like there was nothing to convince them.

"It's the kind of paradox that's inescapable," he said, with a grim humour. "There's very little chance or point trying to dig out of it."

There are many elements of his life that tick the prophetic checklist of his worshippers: a flight from India to the UK as a child, growing up in London, a slight stutter, and appearances on TV. But it is his work that puts him most directly in the frame and causes him the most anguish – the very things the followers of Share believe will indicate that their new messiah has arrived.

Patel's career – spent at Oxford, LSE, the World Bank and with thinktank Food First – has been spent trying to understand the inequalities and problems caused by free market economics, particularly as it relates to the developing world.

His first book, Stuffed and Starved, rips through the problems in global food production and examines how the free market has worked to keep millions hungry (Naomi Klein called it dazzling, while the Guardian's Felicity Lawrence said it was "an impassioned call to action"). The Value of Nothing, meanwhile, draws on the economic collapse to look at how we might fix the system and improve life for billions of people around the globe.

While his goal appears to match Share's vision of worldwide harmony, he says the underlying assumptions it makes are wrong – and possibly even dangerous.

"What I'm arguing in the book is precisely the opposite of the Maitreya: what we need is various kinds of rebellion and transformations about how private property works," he said.

"I don't think a messiah figure is going to be a terribly good launching point for the kinds of politics I'm talking about – for someone who has very strong anarchist sympathies, this has some fairly deep contradictions in it."

To say Patel – with his academic air, stammer and grey-flecked hair – is a reluctant saviour is an understatement. In fact, he rejects the entire notion of saviours. If there is one thing he has learned from his work as an activist in countries such as Zimbabwe and South Africa, it is that there are no easy answers.

"People are very ready to abdicate responsibility and have it shovelled on to someone else's shoulders," he said. "You saw that with Obama most spectacularly, but whenever there's going to be someone who's just going to fix it for you, it's a very attractive story. It's in every mythological structure."

Unravelling exactly what it is that Share International's followers believe, however, is tricky.

The group is an offshoot of the Victorian Theosophy movement founded by Madame Blavatsky that developed a belief system out of an amalgam of various religions, spiritualism and metaphysics.

Creme – who joined a UFO cult in the 1950s before starting Share – has added a cosmic take to the whole concept: he says that Maitreya represents a group of beings from Venus called the Space Brothers.

This 18m-year-old saviour, he says, has been resting somewhere in the Himalayas for 2,000 years and – as a figure who combines messianism for Christians, Buddhists, Hindus, Jews and Muslims alike – is due to return any time now, uniting humanity and making life better for everybody on earth.

Adding to the confusion is the fact that Creme refuses to categorically state whether or not he believes that Patel and Maitreya are one and the same. He suggests that it is not up to him to rule either way, instead blaming media coverage, rather than his own mystical predictions, for making people "hysterical".

"It is not my place," Creme told the writer Scott James, a friend of Patel, recently. "People are looking to Mr Patel because they are looking for the fulfilment of a story which I've been making around the world for the last 35 years."

It is not the first time that Creme, an inscrutable guru with a mop of curly white hair, has courted publicity with his wild pronouncements of a messiah. In 1985 he made another prophecy: that Maitreya would reveal himself to the press in London.

A gaggle of journalists gathered in a Brick Lane curry house for the main event. In the end, the promised saviour failed to materialise. (One candidate, "a man in old robes and a faraway look in his eye", turned out to be a tramp begging for cigarettes, our correspondent wrote at the time).

Patel's rejection of his status as a deity does not seem to have killed off interest from Share's members. Indeed, the situation has invaded his everyday life, such as when two devotees travelled from Detroit – some 2,400 miles away – just to hear him give a short public talk.

"They were really nice people, not in your face, really straightforward – these people do not look like fanatics," he says. "I gave the talk, and they hung around at the end and we had a chat."

It was only then that the pair revealed that they were followers of Creme's teachings.

Patel said: "They said they thought I was the Maitreya … they also said I had appeared in their dreams. I said: 'I'm really flattered that you came all the way here, but it breaks my heart that you came all this way and spent all this money to meet someone who isn't who you think he is.'

"It made me really depressed, actually. That evening I was really down."

While he struggles to cope with this unwanted anointment, his friends and family are more tickled by the situation.

"They think it's hilarious," he said. "My parents came to visit recently, and they brought clothes that said 'he's not the messiah, he's a very naughty boy'. To them, it's just amusing."

There have been similar cases in the past, including Steve Cooper, an unemployed man from Tooting, south London, who was identified by a Hindu sect as the reincarnation of a goddess and now lives in a temple in Gujurat with scores of followers.

Unlike some who have the greatness thrust upon them, though, Patel's greatest hope is that Share will leave him alone so that he can get back to normal life.