Salt the aubergine slices and leave in a colander to remove bitterness. Wash, drain and dry them well.
Heat some olive oil in a wide, non-stick saucepan and sauté the vegetables in the following order: potatoes, courgettes, onions, peppers and finally the aubergines. Remove vegetables with a slotted spoon. Whenever necessary, add oil to the saucepan.
In a bowl, mix tomatoes with parsley, garlic, salt, pepper, sugar and remaining oil. Place sautéed vegetables in a baking pan and pour tomato mixture on top.
Cover with aluminium foil and cook in a pre-heated oven at 200oC for 1 hour. Then remove the aluminium foil, stir the vegetables carefully and put back into the oven to brown. Serve warm accompanied by feta cheese (optional).