A majority of voters are ready to vote for Britain to leave the European Union, according to a shock opinion poll.
The Survation poll for The Mail on Sunday found that if a referendum was held tomorrow 51% would vote to quit the EU against 49% who would vote to remain.
The findings run counter to a string of recent polls which have consistently shown comfortable majorities in favour of staying in.
As recently as July, a Survation poll gave the "in" camp a 54% to 46% advantage.
Politicians will be wary of reading too much into one survey - particularly given the closeness of the margin.
Nevertheless it is likely to set alarm bells ringing in Downing Street ahead of David Cameron's promised referendum - which must take place before the end of 2017.
It will also provide a huge fillip for the "out" campaign ahead of a possible Commons rebellion by Eurosceptic Tories when MPs return to Westminster following the summer break on Monday.
The poll suggested that the margin in favour of leaving could grow if the migrant crisis continues - with 22% of those who said they would vote to stay indicating they could change their minds if the situation worsened.
The poll, of 1,004 people, was carried out by Survation between September 3 and 4.