A Government failure to commission estimates of the numbers of Romanians and Bulgarians who would come to Britain after labour market controls were lifted fuelled "anti-immigrant prejudice", a group of influential MPs have said.
In a damning report, the Home Affairs Select Committee said the Government's decision not to obtain official estimates played into the hands of those who "wish to inflame tensions about immigration for political gain".
Restrictions to the labour market were lifted for Romanians and Bulgarians on January 1, prompting warnings of a looming surge of immigration from the eastern European countries.
But the Committee said the numbers of migrants from the two countries were "more a trickle than a flood".
Committee chair Keith Vaz MP said: " The numbers coming from Bulgaria and Romania since the end of transitional controls appear rather more a trickle than a flood.
"The Government's failure to commission an estimate of these numbers has led to unnecessary anti-immigrant prejudice and is a blot on our tolerant society.
"It is essential that for future enlargement of the EU the Government commission research on the impact of migration to the UK. If they do not do so, the Committee will."
A range of polarised reports emerged in the run-up to the lifting of controls for Romanians and Bulgarians including a predicted surge in pickpocketing, muggings, beggars on the streets and rioting.
Other reports suggested citizens from the two Eastern European countries will attempt to sell their babies when they arrive in Britain.
And claims o f fully-booked flights and coaches from Bucharest and Sofia at the turn of the year were incorrect and retracted.
In its report, the Committee said it was concerned that the decision not to commission estimates "has increased anti-immigrant prejudice and has been commandeered by those who wish to inflame tensions about immigration for political gain".
The group of MPs have recommended that the Government commission its official migration advisers, the Migration Advisory Committee (Mac), to carry out research on the number of Romanians and Bulgarians in the UK.
Romanians and Bulgarians who arrived during the transitional period from January 2007 to December 2013 should be assessed, while the number who arrived since January 1 this year should be considered in a separate study.
"The Committee has seen no evidence to suggest that there has been an increase in migration from Romania and Bulgaria. It would appear rather more a trickle than a flood," the report adds.
In the future, the MPs said, the Mac should provide estimates for expected arrivals from countries involved in any future enlargements of the European Union
Elsewhere in its report, the Committee said there was limited evidence of so-called 'benefits tourism' and it appears to be at much lower levels than claimed by the Government.
Prime Minister David Cameron rushed through new measures at the end of last year to ensure EU migrants will be unable to claim out-of-work benefits for their first three months in the UK.
In addition, those found begging or sleeping rough could be deported and barred from re-entry for 12 months unless they can show they have a proper reason to be in the UK, such as holding a job.
Other proposals previously announced in the Government's Immigration Bill will see migrant access to the NHS restricted, while landlords, employers, bankers and DVLA staff will all be expected to take part in checks for illegal immigrants under tough reforms.
An extension of the NHS charging regime was unveiled, which will see overseas visitors and migrants charged for accident and emergency treatment in England.
Migrants will also have to pay for primary care services such as minor surgery carried out by GPs, while prescription charges will be extended.
A Home Office spokeswoman said: "We are building an immigration system that is fair to British citizens and legitimate migrants and tough on those who abuse the system or flout the law.
"Non-EU migration is at its lowest level since 1998.
"We totally reject the Committee's suggestion that not attempting to forecast the number of Romanian and Bulgarians who might come to the UK after the expiry of transitional controls has led to 'anti-immigrant prejudice'.
"Any such forecasts would have lacked all credibility - indeed, the failure of previous attempts to predict likely numbers of EU migrants in the past only contributed to the public's concern about uncontrolled immigration.
"The Migration Advisory Committee said it would not have been sensible or helpful to make guesses ahead of January 1.
"Our reforms to restrict access to the NHS and other benefits mean British citizens can have more confidence that those who come to the UK do so for the right reasons - to work hard and contribute to society."
Shadow Immigration Minister David Hanson said: "The Government's failure to estimate the impact of Romanian/Bulgarian immigration and to take action to prevent foreign criminals entering the UK are the latest in a long line of failures which show David Cameron's rhetoric on immigration does not match the reality.
"This report shows that the Government woefully failed in its primary duty to prepare for the ending of transitional controls on Romania and Bulgaria. Only at the last minute did they take action we had called for and not to have made any estimate of impacts shows a damning lack of planning by Theresa May and David Cameron.
"Not for the first time this Government's failure on immigration allowed scare stories to run and run that could have been avoided with a simple assessment of the facts. In the meantime they have put UK citizens at risk by not fully adopting European co-operation agreements to share information that would stop foreign criminals entering the UK.
"This report shows that the Government's incompetence in managing the immigration system is only matched by its ability to stoke anti-European feeling to the detriment of the British people."