By Jill McGivering BBC correspondent in Madras

There comes a point when you have to stand up and resist

Jayendra Saraswathi, Hindu priest

Christians are only about 2% of the state's population, but many have flocked to convert in recent years, especially low caste Hindus.

Hindu leaders accuse evangelical Christians of bribing the poor with inducements.

Christians say this is untrue. They fear the vaguely worded law will be used to suppress their activities and become a form of religious persecution.

Growing flock

At a Christian service in the state capital, Madras, several thousand people are packed into what appears more like a huge community hall than a church.

Opponents say the new law restricts religious freedom

It's a very emotionally charged atmosphere.

People are standing with their hands raised in worship, shaking and swaying from side to side with their eyes closed and many are crying.

The Assembly of God Church was founded 30 years ago by American missionaries.

Today about 20,000 people worship here and it's about to expand further into new premises.

Pastor Mohun says the rapid expansion is God's work.

"It is what Jesus Christ has commanded as the great commission, go out and preach and everyone must hear this gospel - that is what we want to do," he told the BBC.

'Unfair' tactics

Although Christians make up only a tiny proportion of the state's population, their evangelical zeal is alarming the majority Hindus.

And now the state's chief minister has taken up the Hindu cause, accusing Christians of forcing Hindus to convert with pressure tactics and bribes.

In this land of spiritual darkness, the evangelical church of India and the ECI partnership have laboured together to bring the light of the gospel to this great nation

Evangelical video

Christians say this is totally untrue and there seems to be no concrete evidence of bribes.

They fear the new law will be used to threaten and suppress the church.

The law says that no-one can be baptised without individual permission from state officials.

Jayendra Saraswathi, one of Hinduism's most holy priests and a powerful figure close to India's right wing pro-Hindu central government in Delhi, says: "There comes a point when you have to stand up and resist.

"It came with British rule, it came with Muslims, now it's coming with Christian conversions.

"This is a warning. We're drawing the line."

'Alien' faiths

Right-wing Hindus are also concerned by the strong links between India's evangelical movement and the West.

When a person embraces these alien faiths... it is almost changing your culture

Maniyan, VHP member

An American video celebrates the work of the evangelical church in India.

"In this land of spiritual darkness", it reports, "the Evangelical Church of India and the ECI partnership have laboured together to bring the light of the gospel to this great nation."

The ECI have established 1,500 churches across India, at a rate of one new church every week.

Their target is a church in every Indian village and for influential Hindu groups this is seen as a direct threat to their traditions.

Maniyan is a member of the Vishwa Hindu Parishad (VHP), a powerful grassroots organisation that promotes Hinduism.

Its political wing is the BJP, which leads India's central government.

He believes a law banning "all types of conversion" should be adopted throughout India in order to protect Indian culture.

"When a person embraces these alien faiths, either Christianity or Islam... it is not only a question of a conversion to some other faith, it is not changing your god, it is not changing your book, it is mostly changing your culture," he says.

"We want to protect the cultural identity of our nation."

Caste

Bishop Ezra Sargunam of ECI conducted his latest mass baptism just two weeks ago.

He's threatening to hold his next one in Tamil Nadu to test the new law.

He sees the law as being politically motivated - the work of the new chief minister, Jayalalitha, who wants to curry favour with the Hindu nationalist BJP government in Delhi.

And he accuses Hindu leaders of trying to protect the caste system by stopping low caste Dalits from converting.

"They will not like the Dalits and the tribals and the so-called untouchables to be liberated from social and political oppression," he says.

"They want them to stay like that - only then their caste system will survive."