The ORB survey for the Telegraph found that if the referendum was held now some 52 per cent of respondents would back remaining a member of the EU, with 43 per cent for leave, down five points on the previous poll.
It appears that Remain voters are catching up with Leave supporters in terms of turnout. Some 70 per cent of Brexit supporters told pollsters they planned to vote, the same level as before, but the Remain turnout was up from 61 to 65 per cent. The overall turnout was up three points to 67 per cent.
ORB also found that Leave supporters were slightly more likely to switch to the other side. Some 17 per cent of the campaign's supporters were described as "soft", compared to 14 per cent of those currently planning to vote to Remain.
Sir Lynton Crosby, the election strategist credited with helping the Conservatives win a majority at the last election, wrote in the Telegraph: "This presents a challenging set of circumstances for the Leave campaign. Not only have they lost some of the advantage from more Outers being motivated to turnout that was benefiting them, but the overall proportion of the British public who support the Leave case has also fallen.
"As identified in recent ORB polls, British voters see the economic case as a strong argument for staying in the EU, but they also see the changes to the immigration system as a benefit of leaving. This remains the case in this poll.
"But what this latest poll also shows is that while the Remain campaign are maximising the potential of the economic arguments, the same cannot be said of the Leave campaign and the immigration case. This is simple to see."
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