It is an advert that will be familiar to most Indians. Baba Ramdev, dressed in the saffron robes of a Hindu saint, sits upright, cross-legged, breathing rapidly to move his diaphragm with all the skill of a yoga master. In the background, a voice lists the benefits of the swami’s Hindu lifestyle. Then the scene changes to a boy bathing with bodywash from the swami’s Patanjali range of bathroom products, which includes shampoos, toothpaste and hair oil.

Ramdev’s endorsement means big bucks in contemporary India. His brand of bodywash is in stores nationwide and has quickly come to compete with long-established brands such as Dove and Nivea. The swami regularly appears on billboards and television shows to recommend his products to his millions of followers.

In the past few years Ramdev has become a national business icon, selling hundreds of products from biscuits to aloe vera juice, all claiming to be Indian-made and good for health.

He surged to popularity as a yoga teacher in the past decade, bringing the discipline to the masses on his 24-hour television channel, Aastha. His rise has been accompanied by a revival of Hindu nationalist sentiment in rapidly modernising India. In recent years Ramdev has shared the stage with the prime minister, Narendra Modi, urging supporters to vote for the Hindu nationalist BJP during the election campaign.

Modi, who has recognised the brand value of new-age gurus, has associated closely with a string of holy men, including Sri Sri Ravi Shankar, whose “Art of Living” event in Delhi last month drew millions of followers.

Baba Ramdev has been given the government’s highest level of security protection, and was recently invited by Modi to inaugurate his flagship International Yoga Day.

Baba Ramdev launches Patanjali instant noodles in Delhi last year. Photograph: Hindustan Times/Getty Images

Over the past year, Patanjali estimates it made a total revenue of £530m, more than double its takings the previous year. Ramdev is leading a new generation of business-savvy ascetics in India who are using their spiritual capital to take on the giants of the retail world. Patanjali’s products are cheap, Ramdev says, because the company sources its materials locally, and because the holy man’s legion of followers are an easy market to tap into.

At Big Bazaar in Mumbai, yoga teacher Shanoo Chimulkar has come to buy his favourite Patanjali biscuits and honey. “He’s really doing a good job,” he says, filling his trolley. “If you say ‘yoga’, people think ‘Ramdev’, and he’s using his popularity to teach people about healthy living.”

Chimulkar swears by Ramdev’s products because they are made from local ingredients. “When companies came from outside and started selling in India, that’s when new health problems like diabetes and cholesterol started appearing. People should stick to our traditional way of life.”

Other shoppers are more sceptical. One man approaches a display of Patanjali products to see what the fuss is about. “I find him absolutely repulsive,” he says. “But everybody’s talking about him so I’ve come to see for myself.”

Ramdev has been in the business of converting spirituality into material profit Swami Agnivesh

A store manager says that the Patanjali range has caught the imagination, and a broad range of Indians are experimenting with Ramdev’s products: “All kinds of people are buying Patanjali, regardless of their social class. The products have an advantage because they are cheaper than other brands, but whether the quality is the same, I can’t tell you.” The company has come under scrutiny in parliament recently. Reports of worms and high levels of monosodium glutamate in Ramdev’s instant noodles sparked controversy last year after a food standards authority said the product never received its approval.

Another product called Putrajeevak Beej, which claims to improve women’s fertility, has come under fire for suggesting it could help couples who want sons rather than daughters. Ramdev’s claims that his products can reduce the risk of conditions such as diabetes and Aids have also prompted criticism.

Unsurprisingly, Ramdev’s commercial rise has also provoked criticism from other holy men. A rival ascetic, Swami Agnivesh, criticised Ramdev in an editorial published in the Indian Express last week. He wrote: “Ramdev has been in the business of converting spirituality into material profit … Religion became, in the process, the means for indulging in covetousness. The mega bucks he earned became his entry into politics.”

But the Ramdev name still carries power. Harish Bijoor, a brand strategist, says the name has “sent the shivers out in corporate boardrooms in India”. According to Bijoor, the brand is set to dwarf its competitors because of Ramdev’s smart marketing tactics. “He wears saffron,” Bijoor explains, a colour that is closely associated with the Hindu religion. “That’s a colour that is the flavour of the decade in India today.