Home Office ministers need to order an official assessment of the likely scale of legal migration to Britain should Turkey join the European Union, a Commons committee has urged.
The home affairs select committee also says that much more must be done to improve security on Turkey's borders before it should be allowed to join the EU. The land border with Greece is now the main loophole for irregular migration into Europe with 350 migrants trying to cross it every day in 2010 and more than 75% of trafficked heroin into the EU also flows across its borders.
The MPs' report says that the available forecasts for the likely flow of Turkish nationals to other European countries should it join the EU range from 500,000 to 4.4 million up until 2030. One estimate by Oxford University suggests that the figure could be as low as 60,000 to 70,000 a year to Europe as a whole.
"Current migration of Turkish nationals to the EU has declined to below 50,000 a year but population trends and the gap in living standards could make easier migration within the EU an attractive option for Turkish citizens," says the report published on Monday.
"Given the UK's experience after the 2004 enlargement, when many thousands more migrants arrived than expected, the committee is cautious about allowing Turkish citizens full freedom of movement and supports the government's commitment to applying 'effective transitional controls as a matter of course' for all new member states," says the report.
The Home Office says that there are about 150,000 Turkish nationals living in Britain at present, with about 500,000 people of Turkish origin living in the country altogether. But Germany, Austria, the Netherlands and France all have larger Turkish communities which are more likely to attract a new wave of legal migration.
Current discussions in Brussels assume that Turkey could join the EU in 2020 but no final decisions have been made and there is significant opposition among some member states.
Home Office immigration minister Damian Green, giving evidence to the committee's inquiry, said it was impossible to make any kind of realistic assessment at the moment on the impact of Turkish accession to the EU on likely migration patterns.
He said that "we don't know any of the basic facts", including whether a transitional period under which Britain could restrict the flow of Turkish migrant workers will be put in place. Green also pointed out that Turkey traditionally had much stronger links with Germany than Britain and had an economy which was growing at a faster rate than India, meaning many Turks might well stay at home.
However, the MPs say that, while the Home Office was no doubt wary of attracting criticism for producing inaccurate estimates in the future, they were concerned that no official impact analysis has yet been carried out: "Accordingly we recommend that the Home Office undertakes this piece of work now and updates it as circumstances change."
Ministers do not want to repeat the experience of 2004 when Poland and other east European states joined and an annual net migration prediction of 13,000 proved well wide of the mark.
