The rise of the Green parties

The three-party (i.e. six plus some purely Flemish and Walloon parties) political systems got disturbed by the Green parties (the Dutch-speaking Agalev, now Groen!, and the French-speaking Ecolo) in the 1980's which took a lot of influence after the Marc Dutroux Scandal and the "dioxin affair", a food scandal (chickens containing dioxin levels far above the maximum allowed) which would not have had any major repercussions, had it not erupted just days before the elections.

The rainbow government (1999-2003)

First government since 1958 without the Catholics but with the Greens.

Renewal of the Belgian foreign politics. Strong anti-Iraq-war diplomacy during the Iraq crisis of 2003.

In July 1999, Belgium's nuclear phase-out legislation was decided by the Flemish Liberals and Democrats-led Government including the Belgian Greens party, Groen!. The phase-out law calls for each of Belgium's seven reactors to close after 40 years of operation with no new reactors built subsequently. When the law was being passed, it was speculated it would be overturned again as soon as an administration without the Greens was in power . After a new government was elected in 2003 without the Greens, there is still no indication the current Government will revoke the phase-out law after the incident at Tihange in November 22, 2002 turned public opinion against nuclear power
 
  Source http://en.wikipedia.org