Illegal immigrants will find it "even easier" to enter the EU if Turkey is allowed to become a member before its border controls are strengthened, MPs have warned.
They fear that the country could be used as a gateway into the union and raised concerns about people trafficking and drug smuggling.
In a report out today the influential Commons Home Affairs Select Committee called for Turkey to be made to demonstrate that it has met stringent border control rules set by Brussels before accession.
Turkey's membership would extend the EU's external border up to Iran, Iraq and Syria.
The report said the land border between Greece and Turkey constitutes the main loophole for irregular immigration into the European Union.
Thousands of migrants are entering the EU through Turkey every month, many aiming to reach the UK, it added.
But the committee said it believed that the risks posed in relation to organised crime were "considerably outweighed" by the potential benefits of Turkey joining, mainly because of the opportunities that it would bring for increased cooperation.