David Cameron has been dealt a fresh blow in his renegotiation with the EU after Poland's Prime Minister Beata Szydlo said she did not see "eye to eye" with the Conservative leader over his proposal to curb welfare benefits. Szydlo urged Cameron to respect the EU's "free movement of peoples" principle over his plan to stop EU migrants from claiming social security payments until they have spent four years in the UK.

But the Polish premier did leave the British prime minister with some hope as she promised to work with his government to tackle welfare tourism. "We fully accept the right of Great Britain to take sovereign decisions with regards welfare policy," The Financial Times reported her saying. "There is a common direction and the future discussions in January will only take us closer to a solution."

The comments come after European Commission (EC) President Donald Tusk warned that there was "no consensus" among EU leaders over Cameron's welfare plans and that the UK's referendum, which will be held in 2016 or 2017, could destabilise the political and economic union.

"Uncertainty about the future of the UK in the EU is a destabilising factor. That is why we must find a way to answer the British concerns as quickly as possible," Tusk said in a letter to the EC.

"In times when geopolitics is back in Europe, we need to be united and strong. This is in our common interest and in the interest of each and every EU member state. The UK has played a constructive and important role in the development of the EU and I am sure that it will continue to do so in the future."

Meanwhile, Cameron played down the setback and argued that the negotiations will take time. "We don't yet have agreement, it is going to take time, but I do feel we have the goodwill to reach an agreement that will be of benefit to the British people."

The latest opinion poll from YouGov, of more than 1,600 people between 19 and 24 November, found that 'remain' was two points ahead of 'leave' (40% versus 38%, respectively). A separate survey from Ipsos MORI for The Economist, of more than 1,000 voters between 30 October and 9 November, found that immigration topped the concerns of the British public.