London (AFP) - A new opinion poll published Sunday showed the number of Britons wanting to leave the European Union rising in the wake of the Paris terror attacks and Cologne assaults.

The poll put the EU exit camp in the lead by 53 percent to 47 ahead of a referendum promised by the end of 2017, but which could take place as early as June.

The Survation poll for the centre-right, eurosceptic, Mail on Sunday newspaper excludes undecided voters.

If they are included, 42 percent are in favour of leaving, 38 for remaining with 20 percent yet to make up their mind.

The survey, which was conducted online on January 15 and 16 and had 1,004 respondents, had a margin of error of two percentage points.

Survation's last poll published in September showed 49 percent in favour of staying, and 51 percent for leaving when undecided voters were excluded.

Some 34 percent said November's Paris terror attacks made them more likely to vote to leave the EU, as opposed to 12 percent who said it would influence them to vote to stay in.

And 38 percent said reports that women were sexually assaulted as part of during Cologne's New Year celebrations meant it was more likely they would vote to leave, as opposed to eight percent who said it would encourage them to remain.

Prime Minister David Cameron has said he will campaign to stay in the European Union only as long as he can negotiate a series of EU reforms intended to restore more sovereignty powers to Britain.

Cameron has said he is reasonably confident of a deal in February on the changes he is seeking in four key areas.