The government has been urged to set aside more money to help public services cope with a possible rise in immigrants from Eastern Europe.
The Institute for Public Policy Research says housing, the NHS and policing will all be stretched if large numbers arrive from Bulgaria and Romania when restrictions lift next week.
ITV News Political Correspondent Carl Dinnen reports from Harrow, one of London's most diverse boroughs:
Britain's economy will be billions of pounds worse off if the Conservatives meet their target of getting annual net immigration below 100,000, a report has warned.
Keeping immigration numbers in five figures would slash 11 percent - or about £165 billion - off UK GDP by the year 2060, said the National Institute for Economic and Social Research think tank.
It said national finances would be hit because immigrants tend to be younger than the national average and can fill gaps in the labour force left by Britain's ageing population, while consuming less than the average Briton in public services.
The report's co-author Katerina Lisenkova said: "Unfortunately, very often on this issue opinions trump evidence."
The Government should be preparing for the impact Bulgarian and Romanian migrants will have on schools and housing instead of alarming the public and announcing "symbolic gestures", a report said.
The UK will be able to absorb the expected influx of migrants next year if ministers adopt contingency measures to deal with pressures arising in local areas, the centre-left think tank Institute for Public Policy Research (IPPR) said.
EU restrictions on movement of Bulgarians and Romanians will be lifted on January 1.
A Tory MP has lablelled Business Secretary Vince Cable's comparison of the Conservatives to Enoch Powell "unacceptable and ridiculous".
Amber Valley MP Nigel Mills criticised the Liberal Democrat minister for "effectively" comparing his coalition partners to the controversial Tory right-winger and his "rivers of blood" speech on immigration.
Mills told BBC Radio 4's Today that Cable's comments made "it very hard to sit around the Cabinet table".
"These comments, coming on the back of some completely sensible policy announcements by the Prime Minister, look completely out of touch with the sentiments of most British people," said Mills.
Vince Cable is not discerning enough when it comes to migration and "pats everyone on the head", warned a migration expert.
Migration Watch's Alp Mehmet dismissed the Business Secretary's criticism of the EU migrant worker cap and suggested he was out of touch with ordinary voters.
The Vice Chairman of the migration think tank was critical of a relaxed attitude towards foreign workers and stood behind the cap.
"It is possible that we will need to do that [migration cap]...even putting a cap still means a hell of a lot of immigration."
– David Hanson, shadow Immigration Minister, labour
The Government is hopelessly split on its approach to the end of transitional controls on Dec 31 for Bulgaria and Romania.
Rather than deal with genuine concerns in a calm and measured way the Prime Minister has sought headlines and panicked on issues he could have dealt with much earlier ...
Instead we have the chaos of the Prime Minister and Home Secretary pretending to pull up the draw bridge and the Lib Dems doing nothing to reform the labour market - both approaches deeply damaging to Britain and local workers.
The Business Secretary "supports" government policy, a Downing Street has said, after Vince Cable suggested that the Conservative Party were doing "a great deal of damage" on their position on immigration. The No 10 source said:
The PM set out his view on EU migration in the FT article and, on Friday, in Brussels. We need to learn the lessons from Labour's mistakes, to put in place more robust transitional controls in future and, in the meantime, to make sure people can come here to work but not just to claim benefits.'
Vince [Cable] is a member of the government and supports government policy. The words he chooses to do that are up to him.
Business Secretary Vince Cable has said the Conservative party are "in a bit of a panic" on immigration, claiming that their position on the issue is "doing a great deal of damage".
"There is very little evidence of benefit tourism coming from eastern Europe, all the evidence suggests they put far more into the economy in terms of tax than they take out in benefits," he told the BBC's Andrew Marr show.
Cable's Liberal Democrat leader, Nick Clegg, has come out against curbs on EU immigration into the UK, claiming that without freedom of movement the National Health Service would "fall over".
As tensions heighten over the possible "influx" of Bulgarian and Romanians from next month, Bulgaria's president criticised the fear tactics being used by some politicians.
Rosen Plevneliev told the Observer: "You see, of course, Great Britain will make its planning and will take its decisions. But some of them could be right, some of them could be wrong. Some of them are bold and some of them are, I would say, not long-term orientated decisions.
"You want to make a plan for a better future for your citizens in Great Britain. In the past 20 years immigrants in Great Britain contributed heavily to its prosperity, and that is a fact.
"The only thing that is important is not to listen to populist politicians who play on people's fears but to listen to the wise men in Great Britain.
"Listen to the institutions who are giving the facts. University College London has very clear data showing that in the past 20 years immigrants contributed 34 per cent more than they took out. You guys are making profit out of this. So that is really great. Keep it like that."