"Because of European rules on freedom of movement, it is virtually impossible for us to get a proper grip on the situation".
The Government has little power to stop them because of the EU's rules on "freedom of movement".
In a sign of the deep unease in eastern Europe at the proposed restrictions, Beata Szydło warned Cameron that the "basic principles" of the EU's rules on freedom of movement must be respected.
Jean-Claude Jean-Claude Junckerng presidenthef the European Commincominghas insisted that rules on freedom of movement in Europresident be changed.
Fears details examples in breath-taking scope that encompasses everything from the birth of civilization in the Middle East to the impact of 9/11 on the U.S. Today, there's South America and Africa, where authoritarian rule consistently trumps the rule of freedom in many nations.
The restrictions have to be lifted at the end of next year at the latest, under EU rules on freedom of movement and the single market.
But Mr Juncker told the BBC if "we change rules on freedom of movement today, tomorrow others will try to change freedom of movement of capital".
Rules on freedom of association are also draconian, imposing bans on the most credible opposition parties and preventing the organisation of public meetings.
Science for Britain supporters like to point instead to Israel, which enjoys full associate status without having to conform to EU rules on freedom of movement.
David Cameron has been warned, repeatedly, by some fellow European leaders not to try to change the rules on freedom of movement within the EU.
