Left-of-centre is a relative statement. Given that CDU+FDP have a governing majority, this pretty much defines SPD and Greens as left-of-centre.

The SPD, like the rest of Europe's Social Democratic parties, is now Social Liberal. Just like the Greens. They differ in the strength of their ecological positions.

The Left parties are mostly former Communists who have now moved into the Social Democratic space.

But you know all this.

There are three stories about the euro crisis: the Republican story, the German story, and the truth. -- Paul Krugman