Once again, a burgeoning controversy is engulfing the American yoga world – the sprawling exercise-cum-enlightenment industry that has steadily captured the hearts and minds of Americans with its promise of a buff bod and a fast track to Nirvana. The last time we checked in on the nation's "wellness practice of choice", which claims a whopping $6bn in annual revenues, dwarfing martial arts and massage combined, the movement – or rather, industry – was divided over the "naked yoga" trend and accusations of using sex to sell classes.

Now, though, it's not sex, but religion that threatens to knock the yoga world off balance. Religious fundamentalists – Christians on one side, Hindus on the other – say they've had enough of yoga's impact on their respective faiths – and their adherents' wallets. Sinners, they reckon, even relatively affluent yoga devotees, have only so much disposable income available for church- or temple-building, especially now when Americans face slow recovery from a historically deep recession.

And, the complaint goes, if Americans keep spending most of their precious "tithings" on $30 yoga classes, $300 workshops, and exotic $3,000 retreats, how will we keep the lights in our temples and mega-churches on?

Albert Mohler, president of the Southern Baptist Theological Seminary, and a leading Christian theologian, fired the first shot in the new holy war against American yoga last September, when he wrote a blistering article, virtually denouncing the practice as the work of the devil, and warning adherents not to attend yoga classes, whose postures and breathing exercises, he believes, are inseparable from the Hindu cosmos, and dangerously antithetical to Christianity.

It was not long before Mohler's fundamentalist views received some surprising confirmation from Hindus. In November, a small but vocal and fairly influential group of transplanted American Hindus, who are grouped around the Hindu-American Foundation (HAF), launched a "Take Back Yoga" movement to try to draw attention to what they agree are the deeply Hindu and Indian religious roots of yoga, which, they feel, the industry has jettisoned in order to sell yoga to secular mainstream. The controversy reached such a pitch that HAF and its claims were even featured in a front-page story in the New York Times.

And just when you thought things couldn't get any weirder or more overblown, Deepak Chopra, the New Age pop-philosopher and author who has charmed millions of bored and restless suburbanites with his workshops, has recently offered his services as a kind of freelance "referee" to the current dispute. Chopra, who's no theologian but happens to be Indian, challenges the claims of HAF, arguing that yoga actually predates Hinduism and, though originating in his homeland, cannot be properly "owned" by any one religious tradition. He's joined in that critique by the American Yoga Association, which points to a multitude of yoga religious blends, including a Jewish variant, "Torah-Yoga", as well as "Christian Yoga", the latter also a critique of the claims of Mohler and his fellow fundamentalists.

Many of these yoga blends largely adapt the yoga postures – and the underlying yoga theology – to their own religious traditions. For example, some Christian yoga practitioners have redesignated "Salute to the Sun", a popular yoga posture that some religious critics claim is too "paganistic", as "Salute to the Son". Some of their classes also feature Christian hymns and mix the classic yoga postures with "non-denominational" stretching techniques.

Of course, Hindu-Christian squabbling over yoga is not new. While not widely reported, evangelical Christian groups in small-town America have been trying for years to have yoga banned from public-school gym classes, and indeed, from any publicly supported facility, on the implied principle that yoga constitutes a religion, and tax dollars should not be used to support its activities. And when conflicts have threatened to get ugly, yogis have usually offered to strip any vestiges of Hindu religiosity from their class offerings, so as not to offend other, more traditional religious sensibilities.

But the intervention by Mohler, HAF and Chopra have forced this simmering, under-the-radar religious dispute out into the open – a clear indication of just how far-reaching yoga's impact as a grassroots movement – and a prospective financial threat to organised religions – is becoming. Mohler's cudgel is likely to be taken up by other mainstream Christian denominations (even though Sarah Palin, one of America's most visible and popular Christian personalities, is a known yoga practitioner).

So, where does this leave mainstream secular yoga practitioners who, if they can tell the difference between a "Downward-Facing Dog" and a "Dolphin" pose, almost certainly couldn't pronounce their names in Sanskrit? Just when they thought they'd found a congenial, gently spiritual refuge from the rage of organised religion's more zealous adherents, the latter have arrived to disturb their karma.