The Hindu nationalist opposition party tipped to win India's election has sparked concern with a manifesto which, though largely devoted to economic development, setss out uncompromising hardline positions on contentious issues and raises the prospect of a revision of the country's policy on use of its nuclear weapons.

The election, a six-week process which is expected to see more than 600 million people vote, started on Monday with millions in the country's remote north-east going to the polls

Surveys predict a big win for the Bharatiya Janata party (BJP) – whose prime ministerial candidate is the controversial Narendra Modi – though not an absolute majority in the 545-seat lower house of the national assembly.

The long-awaited BJP manifesto includes hundreds of policy initiatives including bullet trains, investment in job creation, water connections for every household, increased local defence production and funds to boost the practice of yoga.

But it was commitments to draft a "uniform civil code" – legislation that would withdraw the rights of India's 150 million Muslims to follow their religion-based law – and to "explore all possibilities" to build a Hindu temple at the bitterly contested site in the northern town of Ayodhya, which drew most attention internationally.

The BJP also says it would move to end the special autonomous status accorded to Jammu and Kashmir, the disputed Himalayan former princedom. The manifesto includes a controversial promise to work for the return of Hindus who left Kashmir when a separatist and then increasingly Islamist insurgency took hold in the late 1980s and early 1990s.

However, it is the prospect of a revision of India's nuclear doctrine, whose central principle is that New Delhi would not be first to use atomic weapons in a conflict, that has worried many in the region and beyond. Party sources involved in drafting the document told Reuters the "no first use" policy introduced would be reconsidered. The policy was introduced after India, then under a BJP government, conducted a series of nuclear tests in 1998. Pakistan, India's neighbour responded within weeks with nuclear tests of its own.

"For a long time there has been an assumption that India would not use nuclear weapons first. Given the existing tensions with Pakistan and the fact that those tensions are likely to rise as US troops leave Afghanistan [at the end of this year], this could well cause stress in Pakistan's security establishment which is really not something anyone [in Washington] desires," said Michael Kugelman, of the Woodrow Wilson International Center.

In an interview last month, Rajnath Singh, the BJP president, told the Guardian the party wanted cordial relations with "all countries in the world".

Though Indian elections are unpredictable, most analysts and all polls indicate a significant BJP win. Economic growth faltered three years ago and the Congress party, in power since 2004, has been hit by a series of graft scandals.

Along with its many pledges to improve the living standards of all Indians, the manifesto unequivocally sets out a nationalist agenda. "In a democracy, everyone is not only free, but also encouraged to voice his or her concerns … However, all this should happen within the framework of our constitution and with the spirit of 'India First'. We have to keep the nation at the forefront of our thoughts and actions. Any activity, which disrupts the integrity of the nation, cannot be in the interest of any segment of the society or any region of the country," it says.

One passage refers to the "power" which lies in " the people of India, in the inner sanctum sanctorum of Mother India" and explains that "what is needed is to ignite the spark and Mother India would rise in her full glory."

However, the manifesto also says the "BJP recognises the importance of diversity in Indian society, and the strength and vibrancy it adds to the nation. India constitutes of all its' people, irrespective of caste, creed, religion or sex."

Singh, the party's president, said the manifesto's release was not simply a formality but a "pledge".

The document gives a glimpse into internal tensions within the BJP, which is an offshoot of a broader Hindu nationalist movement which has its roots in the struggle against British colonial rule, and the party's relationship with the vast RSS (National Volunteer Force), an organisation of activists working on a conservative and religious agenda with 40 million members.

Seema Chishti, a journalist with the Indian Express newspaper, said that the inclusion of Ayodhya, Kashmir and then uniform civil code indicated that "the BJP is not in a position to jettison its Hindu identity or issues".

"These are the things they put on the back burner the last time they were in power … but in this manifesto, they have been reintroduced in a significant way," Chishti said.

Though the 50-plus page document acknowledges the "charismatic leadership of Narendra Modi", the promotion of the three-term chief minister of Gujarat on the national stage has been controversial within the BJP.

Modi came from the ranks of the RSS but has distanced himself from the organisation and has caused anger among traditionalist adherents of a vision of India as economically self-sufficient with its emphasis on attracting foreign investment from global firms. Analysts have said that the 63-year-old has sidelined older members of the BJP.

Prof Sumantra Bose of the London School of Economics downplayed any split and said that issues such as Ayodhya, the status of Jammu and Kashmir and the Indian civil code were at "the core of the beliefs of Hindu nationalist leaders of both the generations."

One question is the extent to which the nationalist views would define policy when in power.

"There's a religious right in the BJP so they want to acknowledge that without making it the centrepiece of the manifesto," said Ashok Malik, a political columnist. "I don't think the BJP is going to take it forward as a political movement."

One of the most polarising politicians in India for years, Modi is seen by critics as an extremist who, when chief minister in 2002, was accused of allowing or encouraging mobs to attack Muslims in towns across Gujarat after a lethal fire supposedly started by Muslims on a train full of Hindu pilgrims. Modi denied the allegations and investigators found no evidence of any direct involvement in violence.

He is also accused of an authoritarian style of government at odds with India's tradition of political compromise and consensus-building.

Supporters, including some of the most powerful industrialists in India, say Modi is an honest and decisive administrator who has introduced policies that have encouraged development in his state and could be reproduced elsewhere if he were prime minister. "There should be a strong government in Delhi so that the world doesn't threaten us. We need to hold our heads high and match the world," Modi said in Delhi."