Illegal immigrants to the United States cost the federal government over $10 billion a year, but that figure would increase almost threefold if they were granted legal status, according to a study released on Wednesday. The study by the Center for Immigration Studies, a Washington think-tank which advocates slowing legal immigration and clamping down on illegal migration, measured the amount of revenue illegal immigrants provide through taxes against the government services they and their families consume. There are an estimated 10 million illegal aliens in the United States. "Households headed by illegal aliens imposed more than $26.3 billion in costs on the federal government in 2002 and paid only $16 billion in taxes, creating a net fiscal deficit of $10.4 billion, or $2,700 per illegal household," Steve Camarota, author of the report. These costs, derived from Census Bureau figures, include Medicaid, which provides medical insurance for the poor, other emergency medical treatment, food assistance programs and the federal prison system, where roughly 17 percent of inmates are illegal immigrants. --MORE 2147 Local Time 1847 GMT