BERLIN (Reuters) - The German election race heated up on Thursday as the lead of the centre-left Social Democrats (SPD) over Chancellor Angela Merkel's conservatives narrowed to just four points, three days before the federal election.

       The SPD, whose candidate for chancellor Olaf Scholz is currently vice chancellor and finance minister in Merkel's grand coalition, slipped one point to 25%, according to the Kantar poll.

       Support for the conservative CDU/CSU alliance, whose chancellor candidate is Armin Laschet, rose one percentage point to 22%, while the Greens slipped a point to 16% and the business-friendly Free Democrats (FDP) was stuck at 11%.

       Merkel, in power since 2005, plans to stand down after the election. The SPD's Scholz is German voters' most popular choice by far to succeed her as chancellor.

       (Reporting by Emma Thomasson, editing by Thomas Escritt)