The trades unions say that once in office the liberal, Flemish nationalist, Flemish Christian democrat coalition will make swinging cuts that will above all hit workers and those on benefit.
"This will be the most conservative government since the Second World War”, Mr De Leeuw told journalists.
"Everything is going to be financed on the back of the workers, while the rich and companies will be spared. The measure we already know about are blind cuts that will cost 50,000 jobs. Moreover, skipping an index-linked pay increase will cost those in employment around 20,000 over the duration of their working lives.”
The unions demand that the new federal government guarantees purchasing power, invests in jobs and works toward a fairer taxation system.
The unions add that the measures taken by the new Flemish government also hit those in employment the hardest.
The demonstrators, 5,000 according to the unions, gathered on the Muntplein in front of the Brussels Opera House. Many had travelled to the capital by train and walked to the Muntplein, causing some traffic problems en route.