The French writer André Malraux once asked Jawaharlal Nehru, India's first prime minister, what his greatest challenge had been since independence. "Creating a just state by just means," he replied. Then, after a pause, he added: "Perhaps, too, creating a secular state in a religious country."

India has always been a deeply religious ­nation. Four of the world's major faiths - Hinduism, Buddhism, Sikhism and Jainism - emerged there. Today, it has the third-largest Muslim population on earth, at roughly 150 million, and there are also about 30 million Christians. Though four out of five Indians are Hindus, each of the other major faiths constitutes a majority in one or more of the country's provinces: for example, the Sikhs in Punjab, the Christians in Nagaland and the Muslims in Jammu and Kashmir.

But more than six decades on from independence, India remains an avowedly secular nation state. The preamble to its constitution says: "We, the people of India, having solemnly resolved to constitute India into a sovereign, socialist, secular democratic republic . . .'' The word "secular" was inserted in a 1976 constitutional amendment, in order to make the position explicit.

The constitution does not, however, define what it means by "secular", and nor have the judges of the country's Supreme Court ever settled on an official definition. The Hindi word that is commonly used for secularism in India is dharmanirapekshata, which means "indifference towards religion".In the words of the political scientist Ashutosh Varney, this indifference translates - in theory, if not in practice - "into religious equidistance, not non-involvement". Religions are cherished and valued, and are part of public life, but they have no claims over one another, nor to state or political power.

“In the Indian context, secularism means something quite different from what it does in Europe," Soumya Bhattacharya, editor of the Mumbai-based Hindustan Times, tells me. "Over here, it connotes a tolerance of all religions and actively working towards the coexistence of different religions. In India, a religious person can, and should, be secular."

Divide and rule

Such a view might seem odd in Europe, where the French model of laïcité, for example - often described as the most extreme interpretation of western secularism - is based on a strict separation between state and organised religion. In contrast, the Indian model does not see a wall of separation between politics and faith but, instead, insists on the neutrality of the state towards religion. Indian secularism does not require the state to be irreligious or anti-religious; nor does it ban religion from the public sphere, as is the case in France.

But does such a model of secularism work in practice? "India shows that it is possible, warts and all, to have a functioning, secular judiciary and legal system and to refuse the idea that one religion or sect - be it Hinduism in India or Anglicanism in the UK - gets to set the terms of debate," says Priyamvada Gopal, the Indian-born author and Cambridge University lecturer.

Some in the west assume that the British bequeathed to India its secular fabric, along with democracy, the rule of law and the railways. But this simplistic view ignores the Raj's "divide-and-rule" strategies, which tended to exacerbate rather than reduce tensions between faiths, particularly Hindus and Muslims. The reality, Gopal argues, is that India's state-­sponsored secularism "found subcontinental resources to draw on in the form of an existing heterogeneity and traditions of tolerant, everyday coexistence" between communities.

Separation between faith and state is an ancient feature of Indian society. According to Hindu tradition, there is a split in authority between priest and ruler, the Brahmin and the Kshatriya. "It is an undoubted fact that in India, religions and philosophical thinkers were able to enjoy perfect, nearly absolute freedom for a long period," wrote the sociologist Max Weber in The Religion of India in 1915. "The freedom of thought in ancient India was so considerable as to find no parallel in the west before the most recent age."

Secularism, as leaders of the Indian independence movement such as Mahatma Gandhi, Maulana Abul Kalam Azad and Nehru recognised in the 1930s and 1940s, was not an alien ideology, but "an inextricable part of the nationalist self-conception at independence", says Shabnum Tejani, lecturer in south Asian history at the School of Oriental and African Studies in London. But while Gandhi (a Hindu) and Azad (a Muslim) embraced secularism from their respective religious perspectives, the atheist Nehru was the first to accept it in a political sense. On 3 April 1948, he declared in the Constituent Assembly that: "The alliance of religion and politics . . . is a most dangerous alliance, and it yields the most abnormal kind of illegitimate brood."

In the years after independence in 1947, the idea of India as an inclusive, secular, democratic state became an article of faith among the country's political and cultural elite. Supporters of secularism point to the success that the country has had in enshrining the rights of minorities in law, while also allowing faith communities the freedom to opt for a (voluntary) system of "personal law" on certain family issues, such as marriage and divorce, governed by their respective religious laws. Meanwhile, religious diversity in the public sphere has flourished. The former president of India A P J Abdul Ka­lam is a Muslim, as have been two other former heads of state; the current prime minister, Manmohan Singh, is a Sikh; the head of the Congress Party (and arguably the most powerful person in the country), Sonia Gandhi, is a Roman Catholic.

End of an era

It is important not to romanticise modern, secular India, however. Muslims are among the most deprived communities in the country, with lower-than-average life expectancies and literacy rates. The ghettoisation of Muslim and Christian communities is growing. India's secularism is also riddled with contradictions. Religious festivals, such as Diwali, Eid and Christmas, may not have been granted the status of national holidays, but the state offers various perks to faith communities. The government subsidises air fares for Muslim passengers travelling to Saudi Arabia for the annual hajj pilgrimage (to the tune of roughly 50,000 rupees, or £700, per passenger). "India has evolved to a situation where secularism means treating individual religious communities, especially the Muslims, as requiring special treatment," says Meghnad Desai, the Indian-born Labour peer and author of The Rediscovery of India.

This has long been the challenge from the Hindu right, which alleges that the Indian secular model as advanced by Nehru and his heirs is "western" and "anti-Hindu", "appeases minorities" and is, therefore, "pseudo-secular". One main complaint of right-wing Hindu politicians is the lack of a uniform civil code for all citizens. They point to the anomaly of Muslims being allowed up to four wives under their "personal law", while non-Muslim Indians are legally bound to be monogamous.

Secularism, warns Bhattacharya, is "under threat" - from the rise of Hindu nationalism and militant Islam. The former is heightened by the presence in the political mainstream of the Bharatiya Janata Party (BJP), which is affiliated to the Hindu far right, and the latter by the worrying emergence of home-grown Muslim jihadist groups such as the Indian Mujahideen. Bhattacharya points to the Hindu-Muslim riots of the early 1990s, in which approximately 1,000 people were killed in Mumbai after the demolition of a mosque in the Hindu holy city of Ayodhya, and the pogrom against Muslims in the state of Gujarat in 2002, which led to the deaths of an estimated 2,000 people.

So, is the era of Indian secularism over? On the contrary: the Indian public reaffirmed its commitment to secularism in the general election of 2009, which brought resounding victory to the Congress Party and its secular allies and a crushing defeat for the BJP. Even critics, including Desai, acknowledge that it has virtues worth emulating here in the west. "The Indian stance of empowering communities as having some autonomy within the law could be copied by Europeans - as long as we are sure that the basis of human rights as individualistic is retained," he tells me. Others are more sympathetic. "It's not perfect and perhaps it should be regarded as a work in progress," Gopal says, "but the basic model is worth defending."

Ultimately, a diverse polity such as India can prosper only if it has faith in the inclusive and religiously neutral model of governance established by its founders in 1947. As Gopal says, this model of secularism is "integral to the survival of a nation cobbled together from such a diverse range of faiths, practices, beliefs, identities and languages".