An illegal immigrant in India is a person residing in the country without an official permission as prescribed by relevant Indian law. Those who are explicitly granted refugee status do not fall under this category.
No reliable numbers on illegal immigrants are currently available.
2001 India Census Gives information about Migrants but not exclusively Illegal Immigrants. Per 2001 Census Bangladeshi form the largest group of migrants in India followed by Pakistan.
As per 2001 census there are 3,084,826 people in India who came from Bangladesh No reliable numbers on illegal immigrants are currently available. Extrapolating the census data for the state of Assam alone gives a figure of 2 million. Figures as high as 20 million are also reported in the government and media. Samir Guha Roy of the Indian Statistical Institute called these estimates "motivatedly exaggerated". After examining the population growth and demographic statistics, Roy instead states that while a vast majority are illegal immigrants, significant numbers of internal migration is sometimes falsely thought to be immigrants. An analysis of the numbers by Roy revealed that on average around 91000 Bangladeshis illegal crossed over to India every year during the years 1981-1991
The trip to India from Bangladesh is one of the cheapest in the world, with a trip costing around Rs.2000 (around $30 US), which includes the fee for the "Tour Operator". As Bangladeshi are cultural similar to the Bengali people in India, they are able to pass off as Indian citizens and settle down in any part of India to establish a far better future than they could in Bangladesh, for a very small price. This false identity can be bolstered with false documentation available for as little as Rs.200 ($3 US) can even make them part of the vote bank.
Most of the Bengali speaking people deported from Maharashtra as illegal immigrants are originally Indian citizens from West Bengal. Police would demand 2000-2500 from each of the detained Bengali speaking people for their release. If they fail to pay that amount, they are kept behind the bar for 10–15 days following which they would be taken to border and pushed into Bangladesh.
The Bangladesh Liberation War and continued political and economic turmoil in Bangladesh in the following decades forced some Bangladeshis to seek refuge in India. During the Bangladesh Liberation War at least 10 million Bangladeshis crossed into India illegal to seek refuge from widespread rape and genocide. Most of them migrated to the border states, particularly West Bengal and Assam. This issue became more visible after the 1991 census when patterns of abnormally high growth rate of Muslims were observed in the border states Assam and West Bengal. In 1991 census Muslim population growth rates in these states were found to be much higher than the growth rates of the local Hindu population even after adjusting for the usual higher growth rate of Muslims observed throughout the country. See the following tables for detail.