Labour appears to be the main beneficiaries of David Cameron's speech promising an EU referendum yesterday.
In the first poll since the speech was made, Labour climbed two points to 43% while the Tories were unchanged on 31%.
The poll was conducted between 17:00 GMT Tuesday and 17:00 GMT yesterday, so it only paints an incomplete picture of the public's reception to the speech, but it captures the favourable coverage leading up to and following from the speech. Weekend polls will offer a more comprehensive assessment.
The lack of movement in Tory support could reflect public disinterest in the EU as an issue.
Just six per cent of the public see the EU as one of "the most important" issues facing Britain.
However, when asked if they backed the idea of a referendum, YouGov found 63% of respondents said yes, while less than a quarter were opposed to a vote.
Tory polling is also likely to improve as a result of general with media coverage, as several right-wing newspapers offer a more favourable appraisal of the prime minister in the weeks ahead.
Meanwhile, 55 business leaders have written to the prime minister supporting his push for a more "competitive, flexible and prosperous".
Speaking to business leaders in Davos this morning, the prime minister tried to assure delegates that changes at the continental level would make Europe more competitive.
"Let's negotiate a new settlement for Europe that works for the UK and then let's get fresh consent for it," he said.
"It's not just right for the UK. It's necessary for Europe.
"Europe is being out-competed and out-invested – and it's time we make it an engine for growth, not a source of cost for business and complaint for our citizens."