Certainly seems excessive, I would expect those figures on a track day but not road use, even fast road use.
Checked the official figures (see "technical specifications" on the left menu bar) and this is what they say:
Fuel consumption (L/100 km): at 90 km/h 7.7
Fuel consumption (L/100 km): at 120 km/h 9.8
Fuel consumption (l/100 km): urban cycle 12.3
So the worst, around town is about 12L/100km, not your 20L!!!
Do you drive fast all the time and use high revs?
Have you checked the Co2 reading with a gas analyser, this would tell you if it is using too much fuel.