New Delhi: Rashtriya Swayamsewak Sangh chief, Mohan Bhagwat vowed to press ahead with a campaign to convert Muslims and Christians to Hinduism, stoking a sensitive debate that has stalled parliament and threatened Prime Minister Narendra Modi's economic reform agenda.

Bhagwat said India was a "Hindu nation" where many Hindus had been forcibly converted to other religions.

"We will bring back those who have lost their way. They did not go on their own," Bhagwat said in a speech late on Saturday. "They were lured into leaving."

Bhagwat's comments came after BJP said it did not support forced religious conversions and called for an anti-conversion law.

India's 1.2 billion people are predominantly Hindus but there are also about 160 million Muslims and a small proportion of Christians.

Modi is under fire for being slow to rein in hardline affiliate groups that have been accused of promoting a Hindu-dominant agenda that includes luring Muslims and Christians to convert to Hinduism.

This month, a group of Muslims complained that they had been tricked into attending a conversion ceremony by Hindu groups, while a Hindu priest-turned-lawmaker of the ruling party planned a conversion ceremony on Christmas Day, although it was cancelled after the prime minister intervened.

Supporters define such events as a "homecoming", saying that families signing up for the ceremonies were originally Hindus.

"We don't want to convert anybody ... but then Hindus should also not be converted," Bhagwat said, adding that those who do not support religious conversions should bring in a law against it.

Bhagwat's comments are likely to further irk opposition parties that have disrupted parliament over the conversion issue, demanding that the prime minister himself make a statement on the issue in the upper house.

Although Modi has privately warned lawmakers in his party to back off from controversial issues such as the conversion campaign, he has so far not made any official statement on the subject, leaving it to colleagues to fend off criticism.