Peter Riddell describes this as a bottoming out:
This was bound to happen at some stage as Labour support could not go on falling.It isn't clear that he understands what "bottoming out" is. It or be not be true that Labour support could not go on falling but both would imply that Labour stayed as far behind as it was. Instead it has bounced off the bottom. It may only be three or four per cent of voters who have switched back to Labour but if this happens again the Tory lead will be down to seven points and people will start to doubt whether David Cameron will have any kind of lead by the time of the next election.