The road to spiritual and physical enlightenment can be a lucrative one for the many companies involved in the phenomenal growth of yoga classes, DVDs, books, equipment, clothing. Susie Mesure reports

It is often billed as the ultimate antidote to life in the corporate fast lane. But somewhere along its multi-millennial journey from spiritual practice to gym-class staple, yoga has been subsumed into the very world of big business that its devotees once sought to eschew. The doctrine of renunciation has been lost in the search for a quick buck, according to a new book that exposes the exploitation of an ancient tradition.

Yoga Inc., by John Philp, highlights what he terms the "hypocrisy" of some of the biggest stars in yoga's firmament and warns that it risks losing the good karma that has attracted millions of acolytes. The popularity of yoga has triggered a boom in companies catering to the perceived needs of its practitioners, which Philp believes is anathema to its original purpose of providing spiritual salvation.

"The industry is dressed up in pseudo-religious robes but it's just a big money-making venture for a lot of people," he explains. "The goal of yoga, after all, is detachment and enlightenment. Much in today's yoga scene seems designed to enlighten our wallets and detach us from our savings. And that's hypocritical."

Philp points the finger at self-appointed yoga gurus such as Bikram Choudhury, "the Master of McYoga" who has spawned a multibillion-dollar empire based on his copyrighted "hot yoga" classes, and companies from Nike to Canada's lululemon athletica that churn out yoga paraphernalia.

"Bikram [as he is almost universally known] is the poster boy for everything that has gone horribly wrong with yoga," said Philp. The billionaire yogi, who lives in California, is renowned for his legal battles to stop fellow yoga teachers from offering similar classes to his. Bikram is the force behind the World Yoga Championships and is lobbying to turn yoga into an Olympic exhibition sport, to the consternation of many.

In Britain, up to half a million people regularly practise yoga, according to the British Wheel of Yoga, the discipline's governing body. New studios are opening all the time and the number of teachers is growing by at least 10 per cent a year, BWY figures show. This year's Yoga Show at Olympia, west London, will see more than 300 exhibitors attempt to make money out of all things yogic.

Helen Smith, the BWY's chair, said she rued yoga's increasing commercialisation. "It makes you wonder what visiting gurus from India must think. It's tosh to think you need to buy certain clothes to do yoga. All you need is a non-slip mat and something loose to wear."

Henrietta Roussoulis, a tri-weekly yoga fan, said she "objected" to studios charging excessive prices and making people think they need to spend vast sums on buying into a lifestyle. "It hasn't really got anything to do with yoga," she added.

But yoga companies such as Triyoga, which has three studios in London and sells its own clothing range, DVDs and books, defend their right to make money. Jonathan Saffin, Triyoga's managing director, said: "There's nothing wrong with it. You just need a commercial balance. Yoga centres need to be able to succeed financially but they do need to be run with integrity." Lululemon's chief executive Christine Day said: "You can call it making money or you can call it having a livelihood."

Schools of yoga: Everything from Anusara to Zhander

Anusara: Started by the American John Friend barely a decade ago, Anusara is now the fastest-growing style of yoga.

Ashtanga: The most physical, and probably the most popular, of all the schools of yoga. Students jump back and forward between set sequences of postures using a technique called vinyasa. Its founder, Sri K Pattabhi Jois, died earlier this year, aged 93.

Bikram: The most prescriptive style, coined and copyrighted by Bikram Choudhury. Its 26 poses and two breathing exercises are performed in studios heated to 41C (105F).

Hatha: An umbrella term that covers all the physical schools of yoga. Expect slow-paced stretches with some simple breathing exercises.

Iyengar: A slow-moving style that focuses on precise alignment of the poses and uses straps, blocks and chairs to perfect each posture. Created by B K S Iyengar.

Jivamukti: Started by David Life and Sharon Gannon in 1984, it combines the physical, philosophical and spiritual aspects of yoga set to music.

Kundalini: Sequences use breathing and chanting to encourage untapped "kundalini" energy held at the base of the spine to move up through the body. One of the oldest forms of yoga but coined in its existing form in 1969 by Yogi Bhajan.

Shadow: A style based on classical yogic and Ayurvedic theory. Devised by Zhander Remete it is one of the most intensive schools of yoga.