UK Polling Report is reporting that Labour has now taken a 5-point lead over the Conservatives in the latest daily YouGov poll.
Although any individual poll can be subject to random variations and therefore have a margin of error, the fact that Labour has now been ahead in the last three consecutive polls suggests that they have now genuinely taken the lead.
The reasons behind the change in fortunes for the main parties are difficult to judge. It could be the increasing realisation amongst members of the public of the reality of spending reductions; it may be the negative publicity surrounding the various ex-Tory staff that have been parachuted into supposedly impartial civil service roles during a pay and recruitment freeze for existing staff; it might also be the impact of the recent controversy over the dramatic proposed increases in tuition fees.
Incidentally, this is the best position for Labour since 2007's election-that-never-was.
UPDATE 17 NOVEMBER: The latest poll from Ipsos/MORI shows a similar picture. This now means that the most recent voting intention survey from every major polling firm has Labour ahead, bar one - ICM - which should be publishing a new poll soon.