NEW DELHI - Indian Hindu groups are luring poor Muslims to convert with offers of cheap food, opposition politicians said on Wednesday, accusing the groups of a “diabolical agenda” to undermine religious diversity.

Religious conversions have become a lightning rod in recent months with Prime Minister Narendra Modi’s rivals demanding that he rein in religious groups affiliated to his Bharatiya Janata Party (BJP) trying promote a Hindu-dominant agenda.

About 250 Muslim slum-dwellers changed their faith at a ceremony in the city of Agra this week. But police registered a case on Tuesday after several of those who converted said they had been misled.

They were offered government identity cards showing them to be below the poverty line and thus entitled to cheap supplies of the staples wheat and rice.

Opposition members of parliament criticised the conversions, saying the ruling party was chipping away at India’s secular constitution.

“This house must be assured the constitution of India will not be violated,” Anand Sharma, leader of the opposition Congress party told parliament. “There is a diabolical agenda.”

Hindu organisations stir unease among India’s minority Muslims who accuse them of a deep-seated bias and say they have become more assertive since the rise to power of the Hindu-nationalist BJP in a stunning election victory this year.

Government minister Mukhtar Abbas Naqvi said the opposition critics must allow the police investigation to go ahead and should not jump to conclusions. “We are as committed to the cause of secularism as anyone else,” he said.

Parliament was paralysed for most of last week after a government minister made derogatory remarks about non-Hindus. Modi rejected demands he fire her, saying she had made a public apology.