British support for remaining in the European Union will fall significantly if Prime Minister David Cameron is not able to achieve safeguards for non-euro zone countries and curbs to welfare payments for migrants, according to a poll on Wednesday.
Cameron has promised to renegotiate Britain's relationship with the bloc ahead of a membership referendum by the end of 2017 and EU leaders are due to hold their first detailed talks on his demands at a meeting in Brussels on Thursday.
Among his proposals are guarantees to ensure London's financial dominance is not challenged by the closer integration of the euro zone and a plan to make EU migrant workers wait four years before they are allowed to claim some state benefits.
The latter has proved most problematic, with officials and diplomats saying it would discriminate between EU citizens on national grounds and is therefore against basic EU law.
A ComRes poll of 1,001 adults for the Open Europe think tank found that of Cameron's key demands, failing to achieve these two produced the biggest swing towards the 'out' camp.
As things stand, 56 per cent of voters surveyed between December 11-13 favoured staying in the bloc and 35 per cent would opt to leave, ComRes said.
But if Cameron does not get protections for non-euro zone countries, support for staying falls to 45 per cent and the number who say they would back leaving rises to 46 per cent.
Similarly, if he fails to win the promised curbs for welfare payments to migrant workers, the number who back staying falls to 48 per cent and those who want to leave rises to 45 per cent.
"Failing to achieve these objectives in the renegotiation poses the biggest risk to the UK's continued membership of the EU," Open Europe, which wants to see Britain in a reformed EU, said in a statement.
"The results of the poll should be a message and a warning to those who have dismissed these reforms and the renegotiation as its outcome could have a huge impact on the referendum."
