The pieces of debris have been found by dog walkers in recent weeks, after the Vale Commons Council used dirt supplied by Ronez to fill in a series of potholes and rabbit holes near the car park at the eastern end of L'Ancresse.
Mr Stewart, the former Commerce and Employment minister, lives nearby, and walks his golden retriever, Max, on the common every day.
He is worried not only for the safety of dogs, but also for runners and children using the area.
'All that earth at Mont Cuet could have been used – but this is just complete stupidity and thoughtlessness.'
Mr Stewart said the only way the 'damage' could be reversed, would be if the current filler was dug out and replaced with top soil.
