Ministers have said they want to cut the number of net migrants from more than 100,000 to tens of thousands.
But the National Institute for Economic and Social Research (NIESR) think-tank found that by 2060 the UK would have lost out almost £165 billion at today's prices, or around £2600 for every person in the country, partly because of lower productivity and tax revenue.
The intervention comes as the two sides of the Coalition continued their war of words over immigration yesterday.
Tory MPs called for Lib Dem Business Secretary Vince Cable's head after he compared their party's approach to Enoch Powell and his controversial "rivers of blood" speech. His comments followed a warning from Nick Clegg that he would block future Tory crackdowns on immigration.
The row comes as the Scottish Government prepares to set out more detail on its plans for a more liberal immigration system in an independent Scotland.
Earlier this week Alistair Carmichael, the Lib Dem Scottish Secretary, warned having different laws in Scotland and the rest of the UK created a "real danger" the UK Government would have to erect border posts.
The NIESR model found keeping net migration to the UK below 100,000 would see 11% cut from the UK's GDP by 2060.
The think tank said migrants helped drive the economy because they tended to be younger, and could boost productivity and tax revenue. They also consumed less than the average Briton in services such as healthcare, researchers said.
Net migration just below 100,000 - rather than the Office for National Statistics's forecast estimate of 200,000 - would also mean the Government would have to increase spending and raise income tax by 2.2 percentage points by 2060.
Workers could expect to enjoy higher salaries because there would be less pressure on wages.
But after tax the amount of money in people's pockets would be 3.3% lower.
Co-author Katerina Lisenkova said: "We find that reducing net migration 'from hundreds of thousands to tens of thousands' will have a strong negative impact on the UK economy. Our simulations necessarily do not take into account the potential social impacts of higher immigration."
The report was released as Conservative backbencher Nigel Mills accused Mr Cable of "unacceptable" behaviour and comments that made it "very hard to sit around the Cabinet table".
Other Tories played down the row. Conservative chairman Grant Shapps said: "Vince Cable's a bit like an old uncle at Christmas - slightly rude, does not always make sense, but he is part of the extended family so you live with it."
Yesterday a report by the Instit-ute for Public Policy Research think tank predicted the UK would be able to absorb the expected influx of migrants from Romania and Bulgaria next year, after restrictions are lifted, as long as measures are in place locally.