The militant Shiv Sena party announced that it had identified 50 Hindu couples with five or more children in the parliamentary constituency of the Indian prime minister, Atal Bihari Vajpayee.

"We will honour these couples at a special function next month by conferring the title 'Awakened Hindu Family'," said the Shiv Sena's state chief, Vijay Tiwari. Couples with more than 10 children would be given gifts of gold or silver.

The call runs counter to the Indian government's policy of controlling the country's burgeoning population by promoting family planning. The "awakening" that the Shiv Sena wants to bring about stems from the belief that India's Muslim population, already estimated to be about 140 million, will overtake the Hindu, even though Hindus account for 85% of India's population, now more than a billion.

Demographic experts assert that high birth rates are related to illiteracy and poverty, and have nothing to do with religious beliefs.

Radical Hindu leaders claim the percentage of Muslims has been rising. Their propaganda finds a response among Hindus who resent the Muslims' separate civil law permitting men four wives - though most Muslims are too poor to practise polygamy, and educated Muslims reject the idea.

"Even Hindus who do not support parties like the Shiv Sena or the ruling Bharatiya Janata party [BJP] believe that most Muslims have four wives and lots of children," said Dipankar Gupta, a sociologist. The issue even figured in the Gujarat state assembly elections last year, with the BJP's chief minister, Narendra Modi, mocking Muslim families for their "25 children each".

Now the BJP's political ally, the Shiv Sena, hopes for mileage in the spectre of the "Muslim population bomb".

Mr Tiwari said: "When the Muslims become 30% of the population democracy and peace will disappear from India. To maintain the social balance, and to save the nation, we are now asking Hindu couples to have a minimum of four children each."

Mr Tiwari claimed there had been a positive response from Hindus in Uttar Pradesh. But analysts are doubtful.