A telephone poll by Ipsos MORI showed 53 % of Britons would vote to leave the European Union in a referendum due on June 23, the Evening Standard newspaper said.
Excluding undecided voters, 47 percent of respondents want to remain in the bloc, the poll for the Evening Standard.
It is the first time that the Out campaign has come out ahead in the monthly Ipsos MORI telephone survey since Prime Minister David Cameron pledged in 2013 to hold a referendum, the newspaper said.
The results mark a major turnaround since a May poll by Ipsos MORI, which found that just 37 percent wanted to leave against 55 percent who wanted to stay.
Several polls have seen the “Leave” camp pushing ahead with a week to go before the June 23 vote. An analysis by JPMorgan researchers on Wednesday showed the “Leave” camp in the lead.