He later studied social science at the Parteihochschule Karl Marx, the party school of the Socialist Unity Party of Germany, and worked as a philosophy lecturer at the Free German Youth-administered Wilhelm Pieck youth academy in Bogensee until 1990.

PDS in 2005, merged with the Electoral Alternative for Labor and Social Justice (WASG) to form a new party, The Left (Die Linke).

After the 2009 state election, which produced a so-called “red-red coalition” composed of the SPD and Die Linke, Christoffers was appointed Minister of Economic Affairs and European Affairs in the 3rd Cabinet of Social Democratic Party (SPD) Minister-President Matthias Platzeck, succeeding Ulrich Junghanns of the Christian Democratic Union.

Christoffers faced criticism from within his party for his support of the continuation of lignite mining in the region of Lusatia in southeast Brandenburg.

In a 2010 interview, Wolfgang Nešković, Die Linke Member of the Bundestag for Cottbus – Spree-Neiße, criticized Christoffers’ position for both environmental and political reasons, arguing that support for lignite mining could result in Die Linke being perceived as being to the right of the SPD, their coalition partner.