Punto transmission noise?

I have a 2001 Punto 1.2 8v which has only done 20000 miles.
When I am driving there is a droning noise like a dry bearing. This happens when the engine is pulling and on also decelerating. The noise stops as soon as the clutch is pressed. There is no noise when the car is stationery. Clutch and gearbox work perfectly.
Can anyone help identify the problem? Thanks