Immigrants have cost UK taxpayers more than £22 million a day for 17 years, a report has claimed.
Migration Watch UK research claims that the public purse was £140 billion worse off between 1995 and 2011 as a result of people moving to Britain.
It follows work by the Centre for Research and Analysis of Migration (Cream), an independent research unit at University College London, last year that showed immigrants had made a "substantial" contribution to public finances since 2000 and those from the European Economic Area had contributed 34% more in taxes than they received in benefits in the decade up to 2011.
Migration Watch UK said it had followed the methodology used by Cream but had changed what it called the "unrealistic assumptions" that had been made in that study, such as suggestions that EEA migrants are only half as likely to claim benefits or tax credits - something it claimed was "highly misleading".
Its report states that findings about the contributions made by EEA migrants are "simply wrong" and rely "on assumptions that employees earn the same as the UK-born population".
"In fact, on less unreasonable assumptions, there was no positive fiscal impact at all from the recent EEA migrant group singled out... for their 'very positive contribution'," it states. "Indeed, migration to the UK continues to have a significant fiscal cost, and recent migrants made no difference to the upward trend."
Cream has strenuously dismissed the claims, insisting the think tank's work is "based on a serious misinterpretation of the methodology we have used in our work, which leads to fundamental mistakes that invalidate their calculations".
Sir Andrew Green, chairman of Migration Watch UK, said: "Our report finally disposes of the immigration lobby's oft-repeated claims that immigration reduces our tax burden.
"The total cost is high and increased dramatically between 1995 and 2011, providing no compensation for the overcrowding of this island which we are experiencing, largely as a result of immigration."