Mike Wooldridge reports for BBC television's Newsnight

As devout Hindus in Ahmedabad rekindle the spirit of Hinduism in the land that gave birth to it, there is little sign of a faith and culture under threat.

But several thousand Hindu holy men, sadhus, who have gathered in the city to chart a strident course for the defence of the faith, are accused of helping to create the climate in which Christians are being attacked.

They claim Hinduism is facing an international conspiracy, fronted by a new wave of Christian missionary activity.

The religious difficulty has become a political issue

Vanniyar Adigal Swami, a member of the militant Vishwa Hindu Parishad, told me people were rising up against centuries of oppression.

"For a thousand years we were slaves, the Christians and Muslims were our rulers, they ruled us, they terrorised us, they exploited our resources, they converted us. We cannot fight the fact, we cannot allow them to repeat history."

Doves and hawks

These men are figures of political influence in today's India, sometimes courted but sometimes also chided by their ideological allies in power.

The divide between doves and hawks in the government has been sharpened by the anti-Christian campaign, and one cabinet minister has resigned. The issue has sometimes seemed to consume the country.

Mrs Staines comforts her daughter at the burial of her husband and sons

Gladys Staines and her family are victims of the growing conflict.

I went with her as she visited the grave where her husband Graham and their nine-year-old son Philip and six-year-old Timothy now lie buried. Graham Staines had worked among the people of Orissa for 34 years.

All three were burnt alive in a station wagon. They were sleeping in it overnight in Manoharpur during an annual Christian event known as the jungle camp. They were, it seems, singled out to be killed, and forced back as they tried to escape.

Brutality and forgiveness

One eyewitness, Mathai Murundi, told me: "I heard noises, when I got up I heard the screams of a child. I tried to come out of the house myself, but three people at my door said they would kill me if I did."

Mr Staines and his sons died in a brutal attack

This was an act of such particular brutality that it has been made the subject of a judicial inquiry. Some of the Hindus in Manoharpur say outsiders had been trying to stir up the conversion issue, but it was not something they saw as a problem.

Mrs Staines is determined to maintain the leprosy home which was the focus of her husband's work with the poor. She is adamant: her husband had not been putting pressure on anyone to convert to Christianity.

Even in the home, only 10 of the 70 patients are Christian. Drawing on a profound evangelical faith, Mrs Staines has said she can forgive the killers of her husband and sons. Their ringleader is said to be associated with a Hindu group.

"I know in a natural way of thinking, you would think that to have your husband and children murdered would not be for the good of mankind, but God has put that in my heart.

"As Jesus forgave the people that crucified him, then I was able to forgive those who have done this to my husband, and I believe it will be for the good of humanity in the long run."

Threat to secularism

One widely touted theory surrounding the campaign to present Christianity as a threat to India is that it is aimed at curbing the political rise of Sonia Gandhi - at targeting the Congress Party leader's Italian and Catholic background to persuade voters that if she were to become Prime Minister, India would fall under foreign, Christian, domination.

After the rape of a nun this church has a continuous police guard

But Congress - and peace marchers, too - have been throwing back the challenge to the Hindu nationalists. They say that what is under threat is not the country's distinctive culture but the pillar of modern India, secularism.

Mani Shankar Aiyer of the Congress Party explains: "They know well enough that what you need to do is cause a lot of concern to a targeted community, and rely on some fanatics to take advantage of that heightened tension, to do the deed that they themselves are too cowardly to do, but would not be unhappy to see being done."

An alien faith?

It is becoming an increasingly political issue, but what India's Christians are resisting strongly is the claim of some Hindu extremists that theirs is an alien faith.

The Christian presence in India goes back centuries before the arrival of western missionaries, and the Indianness of the worship in the Catholic church in Orissa is something commonly found today.

The holy masters gather to re-affirm their faith

But this is another church community feeling vulnerable after one of its number, a nun, said she had been raped. For many, including Youth Church Leader Rakesh Singh, putting a police guard at church gates is not enough to end the sense of insecurity:

"The atmosphere which we had before has now changed. Because the relationship between the Hindus and Christians was very nice before, but due to the Staines incident and what is happening in other places, the same thing is being repeated again and again, the relationship which was there before is not now the same."

Many Indians would say one thing they could never have foreseen is a conflict between Hindus and Christians.

Although they deny a hand in the violence, the ultranationalist groups - according to the BJP's one coalition partners - will have to be reined in.